diff --git a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
index 9eb5ad059a..dc1fba5083 100644
--- a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
+++ b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
@@ -638,6 +638,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper213.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper214.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper218.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper221.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper222.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper225.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper226.cs" />
diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper221.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper221.cs
new file mode 100644
index 0000000000..0474c55126
--- /dev/null
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper221.cs
@@ -0,0 +1,58 @@
+using BizHawk.Common;
+using BizHawk.Common.NumberExtensions;
+
+namespace BizHawk.Emulation.Cores.Nintendo.NES
+{
+	public class Mapper221 : NES.NESBoardBase
+	{
+		IntBuffer regs = new IntBuffer(2);
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER221":
+				case "UNIF_BMC-N625092":
+					break;
+				default:
+					return false;
+			}
+
+			return true;
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			ser.Sync("regs", ref regs);
+			base.SyncState(ser);
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			if (addr < 0x4000)
+			{
+				SetMirrorType(addr.Bit(0) ? EMirrorType.Horizontal : EMirrorType.Vertical);
+				regs[0] = addr >> 1 & 0xFF;
+			}
+			else
+			{
+				regs[1] = addr & 7;
+			}
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			int bank;
+			if (addr < 0x4000)
+			{
+				bank = (regs[0] >> 1 & 0x38) | ((regs[0].Bit(0)) ? ((regs[0] & 0x80) > 0) ? regs[1] : (regs[1] & 0x6) | 0x0 : regs[1]);
+			}
+			else
+			{
+				bank = (regs[0] >> 1 & 0x38) | ((regs[0].Bit(0) ? ((regs[0] & 0x80) > 0) ? 0x7 : (regs[1] & 0x6) | 0x1 : regs[1]));
+			}
+
+			return ROM[(bank << 14) + (addr & 0x3FFF)];
+		}
+	}
+}