diff --git a/pcsx2/CDVD/ThreadedFileReader.cpp b/pcsx2/CDVD/ThreadedFileReader.cpp
new file mode 100644
index 0000000000..e7c12f2449
--- /dev/null
+++ b/pcsx2/CDVD/ThreadedFileReader.cpp
@@ -0,0 +1,360 @@
+/*  PCSX2 - PS2 Emulator for PCs
+ *  Copyright (C) 2002-2021 PCSX2 Dev Team
+ *
+ *  PCSX2 is free software: you can redistribute it and/or modify it under the terms
+ *  of the GNU Lesser General Public License as published by the Free Software Found-
+ *  ation, either version 3 of the License, or (at your option) any later version.
+ *
+ *  PCSX2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ *  PURPOSE.  See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with PCSX2.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "PrecompiledHeader.h"
+#include "ThreadedFileReader.h"
+
+ThreadedFileReader::ThreadedFileReader()
+{
+	m_readThread = std::thread([](ThreadedFileReader* r){ r->Loop(); }, this);
+}
+
+ThreadedFileReader::~ThreadedFileReader()
+{
+	m_quit = true;
+	(void)std::lock_guard<std::mutex>{m_mtx};
+	m_condition.notify_one();
+	m_readThread.join();
+	for (auto& buffer : m_buffer)
+		if (buffer.ptr)
+			free(buffer.ptr);
+}
+
+size_t ThreadedFileReader::CopyBlocks(void* dst, const void* src, size_t size) const
+{
+	char* cdst = static_cast<char*>(dst);
+	const char* csrc = static_cast<const char*>(src);
+	const char* cend = csrc + size;
+	if (m_internalBlockSize)
+	{
+		for (; csrc < cend; csrc += m_internalBlockSize, cdst += m_blocksize)
+		{
+			memcpy(cdst, csrc, m_blocksize);
+		}
+		return cdst - static_cast<char*>(dst);
+	}
+	else
+	{
+		memcpy(dst, src, size);
+		return size;
+	}
+}
+
+void ThreadedFileReader::Loop()
+{
+	Threading::SetNameOfCurrentThread("ISO Decompress");
+
+	std::unique_lock<std::mutex> lock(m_mtx);
+
+	while (true)
+	{
+		while (!m_requestSize && !m_quit)
+			m_condition.wait(lock);
+
+		if (m_quit)
+			return;
+
+		u64 requestOffset = m_requestOffset;
+		u32 requestSize = m_requestSize;
+		void* ptr = m_requestPtr.load(std::memory_order_relaxed);
+
+		m_running = true;
+		lock.unlock();
+
+		bool ok = true;
+
+		if (ptr)
+		{
+			ok = Decompress(ptr, requestOffset, requestSize);
+		}
+
+		m_requestPtr.store(nullptr, std::memory_order_release);
+		m_condition.notify_one();
+
+		if (ok)
+		{
+			// Readahead
+			Chunk blk = ChunkForOffset(requestOffset + requestSize);
+			if (blk.chunkID >= 0)
+			{
+				(void)GetBlockPtr(blk, true);
+				blk = ChunkForOffset(blk.offset + blk.length);
+				if (blk.chunkID >= 0)
+					(void)GetBlockPtr(blk, true);
+			}
+		}
+
+		lock.lock();
+		if (requestSize == m_requestSize && requestOffset == m_requestOffset && !m_requestPtr)
+		{
+			// If no one's added more work, mark this one as done
+			m_requestSize = 0;
+		}
+
+		m_running = false;
+		m_condition.notify_one(); // For things waiting on m_running == false
+	}
+}
+
+ThreadedFileReader::Buffer* ThreadedFileReader::GetBlockPtr(const Chunk& block, bool isReadahead)
+{
+	for (int i = 0; i < static_cast<int>(ArraySize(m_buffer)); i++)
+	{
+		if (m_buffer[i].valid.load(std::memory_order_acquire) && m_buffer[i].offset == block.offset)
+		{
+			m_nextBuffer = (i + 1) % ArraySize(m_buffer);
+			return m_buffer + i;
+		}
+	}
+
+	Buffer& buf = m_buffer[m_nextBuffer];
+	{
+		// This can be called from both the read thread threads in ReadSync
+		// Calls from ReadSync are done with the lock already held to keep the read thread out
+		// Therefore we should only lock on the read thread
+		std::unique_lock<std::mutex> lock(m_mtx, std::defer_lock);
+		if (std::this_thread::get_id() == m_readThread.get_id())
+			lock.lock();
+		if (buf.size < block.length)
+			buf.ptr = realloc(buf.ptr, block.length);
+		buf.valid.store(false, std::memory_order_relaxed);
+
+	}
+	int size = ReadChunk(buf.ptr, block.chunkID);
+	if (size > 0)
+	{
+		buf.offset = block.offset;
+		buf.size = size;
+		buf.valid.store(true, std::memory_order_release);
+		m_nextBuffer = (m_nextBuffer + 1) % ArraySize(m_buffer);
+		return &buf;
+	}
+	return nullptr;
+}
+
+bool ThreadedFileReader::Decompress(void* target, u64 begin, u32 size)
+{
+	Chunk blk = ChunkForOffset(begin);
+	char* write = static_cast<char*>(target);
+	u32 remaining = size;
+	if (blk.offset != begin)
+	{
+		u32 off = begin - blk.offset;
+		u32 len = std::min(blk.length - off, size);
+		// Partial block
+		if (Buffer* buf = GetBlockPtr(blk))
+		{
+			if (buf->size < blk.length)
+				return false;
+			write += CopyBlocks(write, static_cast<char*>(buf->ptr) + off, len);
+			remaining -= len;
+			blk = ChunkForOffset(blk.offset + blk.length);
+		}
+		else
+		{
+			return false;
+		}
+	}
+	while (blk.length <= remaining)
+	{
+		if (m_requestCancelled.load(std::memory_order_relaxed))
+		{
+			return false;
+		}
+		if (m_internalBlockSize)
+		{
+			if (Buffer* buf = GetBlockPtr(blk))
+			{
+				if (buf->size < blk.length)
+					return false;
+				write += CopyBlocks(write, buf->ptr, blk.length);
+			}
+		}
+		else
+		{
+			int amt = ReadChunk(write, blk.chunkID);
+			if (amt < static_cast<int>(blk.length))
+				return false;
+			write += blk.length;
+		}
+		remaining -= blk.length;
+		blk = ChunkForOffset(blk.offset + blk.length);
+	}
+	if (remaining)
+	{
+		if (Buffer* buf = GetBlockPtr(blk))
+		{
+			if (buf->size < remaining)
+				return false;
+			write += CopyBlocks(write, buf->ptr, remaining);
+		}
+		else
+		{
+			return false;
+		}
+	}
+	m_amtRead += write - static_cast<char*>(target);
+	return true;
+}
+
+bool ThreadedFileReader::TryCachedRead(void*& buffer, u64& offset, u32& size, const std::lock_guard<std::mutex>&)
+{
+	// Run through twice so that if m_buffer[1] contains the first half and m_buffer[0] contains the second half it still works
+	m_amtRead = 0;
+	u64 end = 0;
+	bool allDone = false;
+	for (int i = 0; i < static_cast<int>(ArraySize(m_buffer) * 2); i++)
+	{
+		Buffer& buf = m_buffer[i % ArraySize(m_buffer)];
+		if (!buf.valid.load(std::memory_order_acquire))
+			continue;
+		if (buf.offset <= offset && buf.offset + buf.size > offset)
+		{
+			u32 off = offset - buf.offset;
+			u32 cpysize = std::min(size, buf.size - off);
+			size_t read = CopyBlocks(buffer, static_cast<char*>(buf.ptr) + off, cpysize);
+			m_amtRead += read;
+			size -= cpysize;
+			offset += cpysize;
+			buffer = static_cast<char*>(buffer) + read;
+			if (size == 0)
+				end = buf.offset + buf.size;
+		}
+		// Do buffers contain the current and next block?
+		if (end > 0 && buf.offset == end)
+			allDone = true;
+	}
+	return allDone;
+}
+
+bool ThreadedFileReader::Open(const wxString& fileName)
+{
+	CancelAndWaitUntilStopped();
+	return Open2(fileName);
+}
+
+int ThreadedFileReader::ReadSync(void* pBuffer, uint sector, uint count)
+{
+	u32 blocksize = InternalBlockSize();
+	u64 offset = (u64)sector * (u64)blocksize + m_dataoffset;
+	u32 size = count * blocksize;
+	{
+		std::lock_guard<std::mutex> l(m_mtx);
+		if (TryCachedRead(pBuffer, offset, size, l))
+			return m_amtRead;
+
+		if (size > 0 && !m_running)
+		{
+			// Don't wait for read thread to start back up
+			if (Decompress(pBuffer, offset, size))
+			{
+				offset += size;
+				size = 0;
+			}
+		}
+
+		if (size == 0)
+		{
+			// For readahead
+			m_requestOffset = offset - 1;
+			m_requestSize = 1;
+			m_requestPtr.store(nullptr, std::memory_order_relaxed);
+		}
+		else
+		{
+			m_requestOffset = offset;
+			m_requestSize = size;
+			m_requestPtr.store(pBuffer, std::memory_order_relaxed);
+		}
+		m_requestCancelled.store(false, std::memory_order_relaxed);
+	}
+	m_condition.notify_one();
+	if (size == 0)
+		return m_amtRead;
+	return FinishRead();
+}
+
+void ThreadedFileReader::CancelAndWaitUntilStopped(void)
+{
+	m_requestCancelled.store(true, std::memory_order_relaxed);
+	std::unique_lock<std::mutex> lock(m_mtx);
+	while (m_running)
+		m_condition.wait(lock);
+}
+
+void ThreadedFileReader::BeginRead(void* pBuffer, uint sector, uint count)
+{
+	s32 blocksize = InternalBlockSize();
+	u64 offset = (u64)sector * (u64)blocksize + m_dataoffset;
+	u32 size = count * blocksize;
+	{
+		std::lock_guard<std::mutex> l(m_mtx);
+		if (TryCachedRead(pBuffer, offset, size, l))
+			return;
+		if (size == 0)
+		{
+			// For readahead
+			m_requestOffset = offset - 1;
+			m_requestSize = 1;
+			m_requestPtr.store(nullptr, std::memory_order_relaxed);
+		}
+		else
+		{
+			m_requestOffset = offset;
+			m_requestSize = size;
+			m_requestPtr.store(pBuffer, std::memory_order_relaxed);
+		}
+		m_requestCancelled.store(false, std::memory_order_relaxed);
+	}
+	m_condition.notify_one();
+}
+
+int ThreadedFileReader::FinishRead(void)
+{
+	if (m_requestPtr.load(std::memory_order_acquire) == nullptr)
+		return m_amtRead;
+	std::unique_lock<std::mutex> lock(m_mtx);
+	while (m_requestPtr)
+		m_condition.wait(lock);
+	return m_amtRead;
+}
+
+void ThreadedFileReader::CancelRead(void)
+{
+	if (m_requestPtr.load(std::memory_order_acquire) == nullptr)
+		return;
+	m_requestCancelled.store(true, std::memory_order_release);
+	std::unique_lock<std::mutex> lock(m_mtx);
+	while (m_requestPtr.load(std::memory_order_relaxed))
+		m_condition.wait(lock);
+}
+
+void ThreadedFileReader::Close(void)
+{
+	CancelAndWaitUntilStopped();
+	for (auto& buf : m_buffer)
+		buf.valid.store(false, std::memory_order_relaxed);
+	Close2();
+}
+
+void ThreadedFileReader::SetBlockSize(uint bytes)
+{
+	m_blocksize = bytes;
+}
+
+void ThreadedFileReader::SetDataOffset(int bytes)
+{
+	m_dataoffset = bytes;
+}
diff --git a/pcsx2/CDVD/ThreadedFileReader.h b/pcsx2/CDVD/ThreadedFileReader.h
new file mode 100644
index 0000000000..eb520a834a
--- /dev/null
+++ b/pcsx2/CDVD/ThreadedFileReader.h
@@ -0,0 +1,121 @@
+/*  PCSX2 - PS2 Emulator for PCs
+ *  Copyright (C) 2002-2021 PCSX2 Dev Team
+ *
+ *  PCSX2 is free software: you can redistribute it and/or modify it under the terms
+ *  of the GNU Lesser General Public License as published by the Free Software Found-
+ *  ation, either version 3 of the License, or (at your option) any later version.
+ *
+ *  PCSX2 is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ *  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ *  PURPOSE.  See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with PCSX2.
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "AsyncFileReader.h"
+#include "Utilities/PersistentThread.h"
+
+#include <thread>
+#include <mutex>
+#include <atomic>
+#include <condition_variable>
+
+/// A file reader for use with compressed formats
+/// Calls decompression code on a separate thread to make a synchronous decompression API async
+class ThreadedFileReader : public AsyncFileReader
+{
+	ThreadedFileReader(ThreadedFileReader&&) = delete;
+protected:
+	struct Chunk
+	{
+		/// Negative block IDs indicate invalid blocks
+		s64 chunkID;
+		u64 offset;
+		u32 length;
+	};
+
+	/// Set nonzero to separate block size of read blocks from m_blocksize
+	/// Requires that chunk size is a multiple of internal block size
+	/// Use to avoid overrunning stack because PCSX2 likes to allocate 2448-byte buffers
+	int m_internalBlockSize = 0;
+
+	/// Get the block containing the given offset
+	virtual Chunk ChunkForOffset(u64 offset) = 0;
+	/// Synchronously read the given block into `dst`
+	virtual int ReadChunk(void* dst, s64 chunkID) = 0;
+	/// AsyncFileReader open but ThreadedFileReader needs prep work first
+	virtual bool Open2(const wxString& fileName) = 0;
+	/// AsyncFileReader close but ThreadedFileReader needs prep work first
+	virtual void Close2(void) = 0;
+
+	ThreadedFileReader();
+	~ThreadedFileReader();
+
+private:
+	int m_amtRead;
+	/// Pointer to read into
+	/// If null when m_requestSize > 0, indicates a request for readahead only
+	std::atomic<void*> m_requestPtr{nullptr};
+	/// Request offset in (internal block) bytes from the beginning of the file
+	u64 m_requestOffset = 0;
+	/// Request size in (internal block) bytes
+	/// In addition to marking the request size, the loop thread uses this variable to decide whether there's work to do (size of 0 means no work)
+	u32 m_requestSize = 0;
+	/// Used to cancel requests early
+	/// Note: It might take a while for the cancellation request to be noticed, wait until `m_requestPtr` is cleared to ensure it's not being written to
+	std::atomic<bool> m_requestCancelled{false};
+	struct Buffer
+	{
+		void* ptr = nullptr;
+		u64 offset = 0;
+		u32 size = 0;
+		std::atomic<bool> valid{false};
+	};
+	/// 2 buffers for readahead (current block, next block)
+	Buffer m_buffer[2];
+	u32 m_nextBuffer = 0;
+
+	std::thread m_readThread;
+	std::mutex m_mtx;
+	std::condition_variable m_condition;
+	/// True to tell the thread to exit
+	bool m_quit = false;
+	/// True if the thread is currently doing something other than waiting
+	/// View while holding `m_mtx`.  If false, you may touch decompression functions from other threads
+	bool m_running = false;
+
+	/// Get the internal block size
+	u32 InternalBlockSize() const { return m_internalBlockSize ? m_internalBlockSize : m_blocksize; }
+	/// memcpy from internal to external blocks
+	/// `size` is in internal block bytes
+	/// Returns the number of external block bytes copied
+	size_t CopyBlocks(void* dst, const void* src, size_t size) const;
+
+	/// Main loop of read thread
+	void Loop();
+
+	/// Load the given block into one of the `m_buffer` buffers if necessary and return a pointer to its contents if successful
+	/// Writes to `m_status` if `!isReadahead`
+	Buffer* GetBlockPtr(const Chunk& block, bool isReadahead = false);
+	/// Decompress from offset to size into
+	bool Decompress(void* ptr, u64 offset, u32 size);
+	/// Cancel any inflight read and wait until the thread is no longer doing anything
+	void CancelAndWaitUntilStopped(void);
+	/// Attempt to read from the cache
+	/// Adjusts pointer, offset, and size if successful
+	/// Returns true if no additional reads are necessary
+	bool TryCachedRead(void*& buffer, u64& offset, u32& size, const std::lock_guard<std::mutex>&);
+
+public:
+	bool Open(const wxString& fileName) final override;
+	int ReadSync(void* pBuffer, uint sector, uint count) final override;
+	void BeginRead(void* pBuffer, uint sector, uint count) final override;
+	int FinishRead(void) final override;
+	void CancelRead(void) final override;
+	void Close(void) final override;
+	void SetBlockSize(uint bytes) final override;
+	void SetDataOffset(int bytes) final override;
+};
diff --git a/pcsx2/CMakeLists.txt b/pcsx2/CMakeLists.txt
index 17e6af6dcb..6654fbf422 100644
--- a/pcsx2/CMakeLists.txt
+++ b/pcsx2/CMakeLists.txt
@@ -205,6 +205,7 @@ set(pcsx2CDVDSources
 	CDVD/ChdFileReader.cpp
 	CDVD/CsoFileReader.cpp
 	CDVD/GzippedFileReader.cpp
+	CDVD/ThreadedFileReader.cpp
 	CDVD/IsoFS/IsoFile.cpp
 	CDVD/IsoFS/IsoFSCDVD.cpp
 	CDVD/IsoFS/IsoFS.cpp
@@ -224,6 +225,7 @@ set(pcsx2CDVDHeaders
 	CDVD/ChdFileReader.h
 	CDVD/CsoFileReader.h
 	CDVD/GzippedFileReader.h
+	CDVD/ThreadedFileReader.h
 	CDVD/IsoFileFormats.h
 	CDVD/IsoFS/IsoDirectory.h
 	CDVD/IsoFS/IsoFileDescriptor.h
diff --git a/pcsx2/pcsx2.vcxproj b/pcsx2/pcsx2.vcxproj
index 7aee440d76..99bf0c410a 100644
--- a/pcsx2/pcsx2.vcxproj
+++ b/pcsx2/pcsx2.vcxproj
@@ -282,6 +282,7 @@
     <ClCompile Include="CDVD\CsoFileReader.cpp" />
     <ClCompile Include="CDVD\GzippedFileReader.cpp" />
     <ClCompile Include="CDVD\OutputIsoFile.cpp" />
+    <ClCompile Include="CDVD\ThreadedFileReader.cpp" />
     <ClCompile Include="CDVD\Linux\DriveUtility.cpp">
       <ExcludedFromBuild>true</ExcludedFromBuild>
     </ClCompile>
@@ -732,6 +733,7 @@
     <ClInclude Include="CDVD\CompressedFileReaderUtils.h" />
     <ClInclude Include="CDVD\CsoFileReader.h" />
     <ClInclude Include="CDVD\GzippedFileReader.h" />
+    <ClInclude Include="CDVD\ThreadedFileReader.h" />
     <ClInclude Include="CDVD\zlib_indexed.h" />
     <ClInclude Include="DebugTools\Breakpoints.h" />
     <ClInclude Include="DebugTools\DebugInterface.h" />
diff --git a/pcsx2/pcsx2.vcxproj.filters b/pcsx2/pcsx2.vcxproj.filters
index db2e6dd2d4..ee2cd2a1e2 100644
--- a/pcsx2/pcsx2.vcxproj.filters
+++ b/pcsx2/pcsx2.vcxproj.filters
@@ -888,6 +888,9 @@
     <ClCompile Include="DebugTools\MipsStackWalk.cpp">
       <Filter>System\Ps2\Debug</Filter>
     </ClCompile>
+    <ClCompile Include="CDVD\ThreadedFileReader.cpp">
+      <Filter>System\ISO</Filter>
+    </ClCompile>
     <ClCompile Include="CDVD\CsoFileReader.cpp">
       <Filter>System\ISO</Filter>
     </ClCompile>
@@ -1948,6 +1951,9 @@
     <ClInclude Include="DebugTools\MipsStackWalk.h">
       <Filter>System\Ps2\Debug</Filter>
     </ClInclude>
+    <ClInclude Include="CDVD\ThreadedFileReader.h">
+      <Filter>System\ISO</Filter>
+    </ClInclude>
     <ClInclude Include="CDVD\CsoFileReader.h">
       <Filter>System\ISO</Filter>
     </ClInclude>