diff --git a/Source/Core/Core/Core.vcxproj b/Source/Core/Core/Core.vcxproj
index 99f2b19876..79c478f980 100644
--- a/Source/Core/Core/Core.vcxproj
+++ b/Source/Core/Core/Core.vcxproj
@@ -446,6 +446,7 @@
     <ClInclude Include="IOS\ES\ES.h" />
     <ClInclude Include="IOS\ES\Formats.h" />
     <ClInclude Include="IOS\FS\FileIO.h" />
+    <ClInclude Include="IOS\FS\FileSystem.h" />
     <ClInclude Include="IOS\FS\FS.h" />
     <ClInclude Include="IOS\Network\ICMPLin.h" />
     <ClInclude Include="IOS\Network\ICMP.h" />
diff --git a/Source/Core/Core/Core.vcxproj.filters b/Source/Core/Core/Core.vcxproj.filters
index 189b7d2088..d3b4d3be27 100644
--- a/Source/Core/Core/Core.vcxproj.filters
+++ b/Source/Core/Core/Core.vcxproj.filters
@@ -1404,6 +1404,9 @@
     <ClInclude Include="IOS\FS\FileIO.h">
       <Filter>IOS\FS</Filter>
     </ClInclude>
+    <ClInclude Include="IOS\FS\FileSystem.h">
+      <Filter>IOS\FS</Filter>
+    </ClInclude>
     <ClInclude Include="IOS\ES\Formats.h">
       <Filter>IOS\ES</Filter>
     </ClInclude>
diff --git a/Source/Core/Core/IOS/FS/FileSystem.h b/Source/Core/Core/IOS/FS/FileSystem.h
new file mode 100644
index 0000000000..6607c9ab02
--- /dev/null
+++ b/Source/Core/Core/IOS/FS/FileSystem.h
@@ -0,0 +1,173 @@
+// Copyright 2018 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "Common/CommonTypes.h"
+#include "Common/Result.h"
+
+class PointerWrap;
+
+namespace IOS::HLE::FS
+{
+enum class ResultCode
+{
+  Success,
+  Invalid,
+  AccessDenied,
+  SuperblockWriteFailed,
+  SuperblockInitFailed,
+  AlreadyExists,
+  NotFound,
+  FstFull,
+  NoFreeSpace,
+  NoFreeHandle,
+  TooManyPathComponents,
+  InUse,
+  BadBlock,
+  EccError,
+  CriticalEccError,
+  FileNotEmpty,
+  CheckFailed,
+  UnknownError,
+  ShortRead,
+};
+
+template <typename T>
+using Result = Common::Result<ResultCode, T>;
+
+using Uid = u32;
+using Gid = u16;
+using Fd = u32;
+
+enum class Mode : u8
+{
+  None = 0,
+  Read = 1,
+  Write = 2,
+  ReadWrite = 3,
+};
+
+enum class SeekMode : u32
+{
+  Set = 0,
+  Current = 1,
+  End = 2,
+};
+
+using FileAttribute = u8;
+
+struct Metadata
+{
+  Uid uid;
+  Gid gid;
+  FileAttribute attribute;
+  Mode owner_mode, group_mode, other_mode;
+  bool is_file;
+  u32 size;
+  u16 fst_index;
+};
+
+struct NandStats
+{
+  u32 cluster_size;
+  u32 free_clusters;
+  u32 used_clusters;
+  u32 bad_clusters;
+  u32 reserved_clusters;
+  u32 free_inodes;
+  u32 used_inodes;
+};
+
+struct DirectoryStats
+{
+  u32 used_clusters;
+  u32 used_inodes;
+};
+
+struct FileStatus
+{
+  u32 offset;
+  u32 size;
+};
+
+class FileSystem
+{
+public:
+  virtual ~FileSystem() = default;
+
+  virtual void DoState(PointerWrap& p) = 0;
+
+  /// Format the file system.
+  virtual ResultCode Format(Uid uid) = 0;
+
+  /// Get a file descriptor for accessing a file.
+  virtual Result<Fd> OpenFile(Uid uid, Gid gid, const std::string& path, Mode mode) = 0;
+  /// Close a file descriptor.
+  virtual ResultCode Close(Fd fd) = 0;
+  /// Read `size` bytes from the file descriptor. Returns the number of bytes read.
+  virtual Result<u32> ReadBytesFromFile(Fd fd, u8* ptr, u32 size) = 0;
+  /// Write `size` bytes to the file descriptor. Returns the number of bytes written.
+  virtual Result<u32> WriteBytesToFile(Fd fd, const u8* ptr, u32 size) = 0;
+  /// Reposition the file offset for a file descriptor.
+  virtual Result<u32> SeekFile(Fd fd, u32 offset, SeekMode mode) = 0;
+  /// Get status for a file descriptor.
+  virtual Result<FileStatus> GetFileStatus(Fd fd) = 0;
+
+  template <typename T>
+  Result<u32> ReadFile(Fd fd, T* ptr, u32 count)
+  {
+    const Result<u32> bytes = ReadBytesFromFile(fd, reinterpret_cast<u8*>(ptr), sizeof(T) * count);
+    if (!bytes)
+      return bytes.Error();
+    if (*bytes != sizeof(T) * count)
+      return ResultCode::ShortRead;
+    return count;
+  }
+
+  template <typename T>
+  Result<u32> WriteFile(Fd fd, const T* ptr, u32 count)
+  {
+    const auto result = WriteBytesToFile(fd, reinterpret_cast<const u8*>(ptr), sizeof(T) * count);
+    if (!result)
+      return result.Error();
+    return count;
+  }
+
+  /// Create a file with the specified path and metadata.
+  virtual ResultCode CreateFile(Uid caller_uid, Gid caller_gid, const std::string& path,
+                                FileAttribute attribute, Mode owner_mode, Mode group_mode,
+                                Mode other_mode) = 0;
+  /// Create a directory with the specified path and metadata.
+  virtual ResultCode CreateDirectory(Uid caller_uid, Gid caller_gid, const std::string& path,
+                                     FileAttribute attribute, Mode owner_mode, Mode group_mode,
+                                     Mode other_mode) = 0;
+
+  /// Delete a file or directory with the specified path.
+  virtual ResultCode Delete(Uid caller_uid, Gid caller_gid, const std::string& path) = 0;
+  /// Rename a file or directory with the specified path.
+  virtual ResultCode Rename(Uid caller_uid, Gid caller_gid, const std::string& old_path,
+                            const std::string& new_path) = 0;
+
+  /// List the children of a directory (non-recursively).
+  virtual Result<std::vector<std::string>> ReadDirectory(Uid caller_uid, Gid caller_gid,
+                                                         const std::string& path) = 0;
+
+  /// Get metadata about a file.
+  virtual Result<Metadata> GetMetadata(Uid caller_uid, Gid caller_gid, const std::string& path) = 0;
+  /// Set metadata for a file.
+  virtual ResultCode SetMetadata(Uid caller_uid, const std::string& path, Uid uid, Gid gid,
+                                 FileAttribute attribute, Mode owner_mode, Mode group_mode,
+                                 Mode other_mode) = 0;
+
+  /// Get usage information about the NAND (block size, cluster and inode counts).
+  virtual Result<NandStats> GetNandStats() = 0;
+  /// Get usage information about a directory (used cluster and inode counts).
+  virtual Result<DirectoryStats> GetDirectoryStats(const std::string& path) = 0;
+};
+
+}  // namespace IOS::HLE::FS