diff --git a/Core/Core.vcxproj b/Core/Core.vcxproj
index a6178fb8..e0db74c9 100644
--- a/Core/Core.vcxproj
+++ b/Core/Core.vcxproj
@@ -716,6 +716,7 @@
     <ClInclude Include="Types.h" />
     <ClInclude Include="UnifBoards.h" />
     <ClInclude Include="UnifLoader.h" />
+    <ClInclude Include="Unl255in1.h" />
     <ClInclude Include="Unl43272.h" />
     <ClInclude Include="UnlPuzzle.h" />
     <ClInclude Include="VideoHud.h" />
diff --git a/Core/Core.vcxproj.filters b/Core/Core.vcxproj.filters
index 85254acd..825981db 100644
--- a/Core/Core.vcxproj.filters
+++ b/Core/Core.vcxproj.filters
@@ -1129,6 +1129,9 @@
     <ClInclude Include="MMC3_Fk23C.h">
       <Filter>Nes\Mappers\Unif</Filter>
     </ClInclude>
+    <ClInclude Include="Unl255in1.h">
+      <Filter>Nes\Mappers\Unif</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="stdafx.cpp">
diff --git a/Core/MapperFactory.cpp b/Core/MapperFactory.cpp
index 670f2887..4475c697 100644
--- a/Core/MapperFactory.cpp
+++ b/Core/MapperFactory.cpp
@@ -217,6 +217,7 @@
 #include "Txc22211B.h"
 #include "Txc22211C.h"
 #include "TxSRom.h"
+#include "Unl255in1.h"
 #include "Unl43272.h"
 #include "UnlPci556.h"
 #include "UnlPuzzle.h"
@@ -535,6 +536,7 @@ BaseMapper* MapperFactory::GetMapperFromID(RomData &romData)
 		case UnifBoards::Super40in1Ws: return new Super40in1Ws();
 		case UnifBoards::T262: return new T262();
 		case UnifBoards::Tf1201: return new Tf1201();
+		case UnifBoards::Unl255in1: return new Unl255in1();
 		case UnifBoards::Unl43272: return new Unl43272();
 		case UnifBoards::UnlPuzzle: return new UnlPuzzle();
 
diff --git a/Core/UnifBoards.h b/Core/UnifBoards.h
index be50eede..d280d759 100644
--- a/Core/UnifBoards.h
+++ b/Core/UnifBoards.h
@@ -51,5 +51,6 @@ namespace UnifBoards {
 		UnlPuzzle,
 		Fk23C,
 		Fk23Ca,
+		Unl255in1,
 	};
 }
\ No newline at end of file
diff --git a/Core/UnifLoader.cpp b/Core/UnifLoader.cpp
index 6bc7b7f2..5349d5b3 100644
--- a/Core/UnifLoader.cpp
+++ b/Core/UnifLoader.cpp
@@ -7,6 +7,7 @@ std::unordered_map<string, int> UnifLoader::_boardMappings = std::unordered_map<
 	{ "13in1JY110", UnifBoards::UnknownBoard },
 	{ "190in1", UnifBoards::Bmc190in1 },
 	{ "22211", 132 },
+	{ "255in1", UnifBoards::Unl255in1 }, //Doesn't actually exist as a UNIF file (used to assign a mapper to the 255-in-1 rom)
 	{ "3D-BLOCK", UnifBoards::UnknownBoard },
 	{ "411120-C", UnifBoards::Bmc411120C },
 	{ "42in1ResetSwitch", 226 },
diff --git a/Core/Unl255in1.h b/Core/Unl255in1.h
new file mode 100644
index 00000000..b55ba2fc
--- /dev/null
+++ b/Core/Unl255in1.h
@@ -0,0 +1,21 @@
+#pragma once
+#include "stdafx.h"
+#include "BaseMapper.h"
+
+class Unl255in1 : public BaseMapper
+{
+protected:
+	virtual uint16_t GetPRGPageSize() override { return 0x8000; }
+	virtual uint16_t GetCHRPageSize() override { return 0x2000; }
+
+	void InitMapper() override
+	{
+		WriteRegister(0x8000, 0);
+	}
+
+	void WriteRegister(uint16_t addr, uint8_t value) override
+	{
+		SelectCHRPage(0, addr & 0x07);
+		SelectPRGPage(0, (addr >> 2) & 0x03);
+	}
+};
\ No newline at end of file
diff --git a/GUI.NET/Dependencies/MesenDB.txt b/GUI.NET/Dependencies/MesenDB.txt
index 7d9ce9d7..60792702 100644
--- a/GUI.NET/Dependencies/MesenDB.txt
+++ b/GUI.NET/Dependencies/MesenDB.txt
@@ -368,7 +368,7 @@
 1E66861F,Playchoice,,,,1,128,128,,0,0,0,,,
 1EB4A920,NesNtsc,AVE-NINA-06,NINA-06,,79,32,32,,0,0,0,v,,
 1EBB5B42,NesNtsc,NES-SNROM,NES-SNROM-06,MMC1B2,1,128,,8,8,0,0,,FourPlayer,
-1EC1DFEB,NesNtsc,,,,217,64,32,,0,0,0,v,,
+1EC1DFEB,NesNtsc,UNL-255in1,,,65000,64,32,,0,0,0,v,,
 1ED48C5C,Famicom,HVC-UNROM,HVC-UNROM-09,,2,128,,8,0,0,0,v,,
 1ED5C801,NesPal,NES-TSROM,NES-TSROM-08,MMC3B,4,256,128,,8,0,0,,,
 1ED7D6BE,Famicom,HVC-TLROM,HVC-TLROM-02,MMC3A,4,128,128,,0,0,0,,,