diff --git a/Core/Core.vcxproj b/Core/Core.vcxproj
index 035fd73a..f068284c 100644
--- a/Core/Core.vcxproj
+++ b/Core/Core.vcxproj
@@ -477,6 +477,7 @@
     <ClInclude Include="Mapper234.h" />
     <ClInclude Include="Mapper183.h" />
     <ClInclude Include="Mapper253.h" />
+    <ClInclude Include="MMC3_123.h" />
     <ClInclude Include="MMC3_134.h" />
     <ClInclude Include="MMC3_196.h" />
     <ClInclude Include="MMC3_219.h" />
diff --git a/Core/Core.vcxproj.filters b/Core/Core.vcxproj.filters
index 1dbe4065..12272225 100644
--- a/Core/Core.vcxproj.filters
+++ b/Core/Core.vcxproj.filters
@@ -937,6 +937,9 @@
     <ClInclude Include="Mapper216.h">
       <Filter>Nes\Mappers\Unnamed</Filter>
     </ClInclude>
+    <ClInclude Include="MMC3_123.h">
+      <Filter>Nes\Mappers\MMC</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="stdafx.cpp">
diff --git a/Core/MMC3_123.h b/Core/MMC3_123.h
new file mode 100644
index 00000000..e30616f1
--- /dev/null
+++ b/Core/MMC3_123.h
@@ -0,0 +1,58 @@
+#pragma once
+#include "stdafx.h"
+#include "MMC3.h"
+
+class MMC3_123 : public MMC3
+{
+private:
+	const uint8_t _security[8] = { 0,3,1,5,6,7,2,4 };
+	uint8_t _exReg[2];
+
+	void UpdatePrgMapping() override 
+	{
+		if(_exReg[0] & 0x40) {
+			uint8_t bank = (_exReg[0] & 0x05) | ((_exReg[0] & 0x08) >> 2) | ((_exReg[0] & 0x20) >> 2);
+			if(_exReg[0] & 0x02) {
+				SelectPrgPage4x(0, (bank & 0xFE) << 1);
+			} else {
+				SelectPrgPage2x(0, bank << 1);
+				SelectPrgPage2x(1, bank << 1);
+			}
+		} else {
+			MMC3::UpdatePrgMapping();
+		}
+	}
+
+	void InitMapper() override
+	{
+		MMC3::InitMapper();
+
+		_exReg[0] = _exReg[1] = 0;
+		AddRegisterRange(0x5001, 0x5FFF, MemoryOperation::Write);
+	}
+
+	void StreamState(bool saving) override
+	{
+		MMC3::StreamState(saving);
+		Stream(_exReg[0], _exReg[1]);
+	}
+
+	void WriteRegister(uint16_t addr, uint8_t value) override
+	{
+		if(addr < 0x8000 && addr & 0x0800) {
+			if(addr & 0x01) {
+				_exReg[1] = value;
+			} else {
+				_exReg[0] = value;
+			}
+			UpdatePrgMapping();
+		} else if(addr < 0xA000) {
+			switch(addr & 0x8001) {
+				case 0x8000: MMC3::WriteRegister(0x8000, (value & 0xC0) | (_security[value & 0x07])); break;
+				case 0x8001: MMC3::WriteRegister(0x8001, value); break;
+			}
+		} else {
+			MMC3::WriteRegister(addr, value);
+		}
+	}
+};
\ No newline at end of file
diff --git a/Core/MapperFactory.cpp b/Core/MapperFactory.cpp
index 492c0f30..83349e5b 100644
--- a/Core/MapperFactory.cpp
+++ b/Core/MapperFactory.cpp
@@ -102,6 +102,7 @@
 #include "MMC3_114.h"
 #include "MMC3_115.h"
 #include "MMC3_121.h"
+#include "MMC3_123.h"
 #include "MMC3_134.h"
 #include "MMC3_165.h"
 #include "MMC3_182.h"
@@ -193,7 +194,7 @@ Supported mappers:
 | 64| 65| 66| 67| 68| 69| 70| 71| 72| 73| 74| 75| 76| 77| 78| 79|
 | 80|===| 82|   |===| 85| 86| 87| 88| 89| 90| 91| 92| 93| 94| 95|
 | 96| 97|===| 99|...|101|===|103|   |105|106|107|108|===|===|===|
-|112|113|114|115|   |117|118|119|120|121|===|   |===|   |   |===|
+|112|113|114|115|   |117|118|119|120|121|===|123|===|   |   |===|
 |===|===|===|===|132|133|134|===|136|137|138|139|140|141|142|143|
 |144|145|146|147|148|149|150|151|152|153|154|155|156|157|   |159|
 |---|===|162|163|164|165|166|167|168|===|170|171|172|173|===|175|
@@ -325,6 +326,7 @@ BaseMapper* MapperFactory::GetMapperFromID(RomData &romData)
 		case 119: return new MMC3_ChrRam(0x40, 0x7F, 8);
 		case 120: return new Mapper120();
 		case 121: return new MMC3_121();
+		case 123: return new MMC3_123();
 		case 132: return new Txc22211A();
 		case 133: return new Sachen_133();
 		case 134: return new MMC3_134();