diff --git a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
index 4313a8a8bb..8a2ecc281d 100644
--- a/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
+++ b/BizHawk.Emulation.Cores/BizHawk.Emulation.Cores.csproj
@@ -518,6 +518,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper041.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper042.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper045.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\Mapper051.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper057.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper058.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper069.cs" />
diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper051.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper051.cs
new file mode 100644
index 0000000000..586920c344
--- /dev/null
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/Boards/Mapper051.cs
@@ -0,0 +1,112 @@
+using BizHawk.Common;
+
+namespace BizHawk.Emulation.Cores.Nintendo.NES
+{
+	public sealed class Mapper051 : NES.NESBoardBase
+	{
+		private int _bank;
+		private int _mode = 2;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER051":
+					break;
+				default:
+					return false;
+			}
+
+			SetMirrorType(Cart.pad_h, Cart.pad_v);
+			return true;
+		}
+
+		public override void NESSoftReset()
+		{
+			_bank = 0;
+			_mode = 2;
+			base.NESSoftReset();
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("bank", ref _bank);
+			ser.Sync("mode", ref _mode);
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			int prgBank8k;
+			if ((_mode & 0x02) > 0)
+			{
+				prgBank8k = ((_bank & 7) << 2) | 0x23;
+			}
+			else
+			{
+				prgBank8k = ((_bank & 4) << 2) | 0x2F;
+			}
+
+			return ROM[(prgBank8k  * 0x2000) + addr];
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			int prgBank16k_8;
+			int prgBank16k_C;
+
+			int prgBank;
+
+			if ((_mode & 0x02) > 0)
+			{
+				prgBank16k_8 = (_bank << 1) | 0;
+				prgBank16k_C = (_bank << 1) | 1;
+
+				prgBank = _bank << 1;
+			}
+			else
+			{
+				prgBank16k_8 = (_bank << 1) | (_mode >> 4);
+				prgBank16k_C = ((_bank & 0xC) << 1) | 7;
+			}
+
+			if (addr < 0x4000)
+			{
+				return ROM[(prgBank16k_8 * 0x4000) + (addr & 0x3FFF)];
+			}
+			else
+			{
+				return ROM[(prgBank16k_C * 0x4000) + (addr & 0x3FFF)];
+			}
+		}
+
+		public override void WritePPU(int addr, byte value)
+		{
+			_mode = value & 0x012;
+			SyncMirroring();
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			_bank = value & 0x0F;
+			if ((addr & 0x4000) > 0)
+			{
+				_mode = (_mode & 0x02) | (value & 0x10);
+			}
+
+			SyncMirroring();
+		}
+
+		private void SyncMirroring()
+		{
+			if (_mode == 0x12)
+			{
+				SetMirrorType(EMirrorType.Horizontal);
+			}
+			else
+			{
+				SetMirrorType(EMirrorType.Vertical);
+			}
+		}
+	}
+}