diff --git a/libraries/AP_Filesystem/AP_Filesystem.cpp b/libraries/AP_Filesystem/AP_Filesystem.cpp
index 4488f699ad..a3a8e8933b 100644
--- a/libraries/AP_Filesystem/AP_Filesystem.cpp
+++ b/libraries/AP_Filesystem/AP_Filesystem.cpp
@@ -43,6 +43,9 @@ static AP_Filesystem_Param fs_param;
 #include "AP_Filesystem_Sys.h"
 static AP_Filesystem_Sys fs_sys;
 
+#include "AP_Filesystem_Mission.h"
+static AP_Filesystem_Mission fs_mission;
+
 /*
   mapping from filesystem prefix to backend
  */
@@ -54,6 +57,7 @@ const AP_Filesystem::Backend AP_Filesystem::backends[] = {
     { "@PARAM/", fs_param },
     { "@SYS/", fs_sys },
     { "@SYS", fs_sys },
+    { "@MISSION/", fs_mission },
 };
 
 #define MAX_FD_PER_BACKEND 256U
diff --git a/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp b/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp
new file mode 100644
index 0000000000..5c6512f8cb
--- /dev/null
+++ b/libraries/AP_Filesystem/AP_Filesystem_Mission.cpp
@@ -0,0 +1,247 @@
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*
+  ArduPilot filesystem interface for mission/fence/rally
+ */
+#include "AP_Filesystem.h"
+#include "AP_Filesystem_Mission.h"
+#include <AP_Mission/AP_Mission.h>
+#include <AC_Fence/AC_Fence.h>
+#include <AP_Rally/AP_Rally.h>
+#include <GCS_MAVLink/MissionItemProtocol_Rally.h>
+#include <GCS_MAVLink/MissionItemProtocol_Fence.h>
+
+extern const AP_HAL::HAL& hal;
+extern int errno;
+
+int AP_Filesystem_Mission::open(const char *fname, int flags)
+{
+    enum MAV_MISSION_TYPE mtype;
+
+    if (!check_file_name(fname, mtype)) {
+        errno = ENOENT;
+        return -1;
+    }
+    if ((flags & O_ACCMODE) != O_RDONLY) {
+        return -1;
+    }
+    uint8_t idx;
+    for (idx=0; idx<max_open_file; idx++) {
+        if (!file[idx].open) {
+            break;
+        }
+    }
+    if (idx == max_open_file) {
+        errno = ENFILE;
+        return -1;
+    }
+    struct rfile &r = file[idx];
+    r.file_ofs = 0;
+    r.open = true;
+    r.mtype = mtype;
+    r.num_items = get_num_items(r.mtype);
+
+    return idx;
+}
+
+int AP_Filesystem_Mission::close(int fd)
+{
+    if (fd < 0 || fd >= max_open_file || !file[fd].open) {
+        errno = EBADF;
+        return -1;
+    }
+    struct rfile &r = file[fd];
+    r.open = false;
+    return 0;
+}
+
+/*
+  packed format:
+    file header:
+      uint16_t magic = 0x671b
+      uint16_t data_type MAV_MISSION_TYPE_*
+      uint32_t total_items
+
+    per-entry is mavlink packed item
+ */
+
+/*
+  read from file handle
+ */
+int32_t AP_Filesystem_Mission::read(int fd, void *buf, uint32_t count)
+{
+    if (fd < 0 || fd >= max_open_file || !file[fd].open) {
+        errno = EBADF;
+        return -1;
+    }
+
+    struct rfile &r = file[fd];
+    size_t header_total = 0;
+    uint8_t *ubuf = (uint8_t *)buf;
+
+    if (r.file_ofs < sizeof(struct header)) {
+        struct header hdr;
+        hdr.data_type = uint16_t(r.mtype);
+        hdr.num_items = r.num_items;
+        uint8_t n = MIN(sizeof(hdr) - r.file_ofs, count);
+        const uint8_t *b = (const uint8_t *)&hdr;
+        memcpy(ubuf, &b[r.file_ofs], n);
+        count -= n;
+        header_total += n;
+        r.file_ofs += n;
+        ubuf += n;
+        if (count == 0) {
+            return header_total;
+        }
+    }
+
+    uint32_t data_ofs = r.file_ofs - sizeof(struct header);
+    mavlink_mission_item_int_t item;
+    const uint8_t item_size = MAVLINK_MSG_ID_MISSION_ITEM_INT_LEN;
+    uint32_t item_ofs = data_ofs % item_size;
+    uint32_t total = 0;
+
+    while (count > 0) {
+        uint32_t item_idx = data_ofs / item_size;
+
+        const uint8_t *ibuf = (const uint8_t *)&item;
+        if (!get_item(item_idx, r.mtype, item)) {
+            break;
+        }
+        const uint8_t n = MIN(item_size - item_ofs, count);
+        memcpy(ubuf, &ibuf[item_ofs], n);
+        ubuf += n;
+        count -= n;
+        total += n;
+        item_ofs = 0;
+        data_ofs += n;
+    }
+
+    r.file_ofs += total;
+    return total + header_total;
+}
+
+int32_t AP_Filesystem_Mission::lseek(int fd, int32_t offset, int seek_from)
+{
+    if (fd < 0 || fd >= max_open_file || !file[fd].open) {
+        errno = EBADF;
+        return -1;
+    }
+    struct rfile &r = file[fd];
+    switch (seek_from) {
+    case SEEK_SET:
+        r.file_ofs = offset;
+        break;
+    case SEEK_CUR:
+        r.file_ofs += offset;
+        break;
+    case SEEK_END:
+        errno = EINVAL;
+        return -1;
+    }
+    return r.file_ofs;
+}
+
+int AP_Filesystem_Mission::stat(const char *name, struct stat *stbuf)
+{
+    enum MAV_MISSION_TYPE mtype;
+    if (!check_file_name(name, mtype)) {
+        errno = ENOENT;
+        return -1;
+    }
+    memset(stbuf, 0, sizeof(*stbuf));
+    // give fixed size to avoid needing to scan entire file
+    stbuf->st_size = 1024*1024;
+    return 0;
+}
+
+/*
+  check for the right file name
+ */
+bool AP_Filesystem_Mission::check_file_name(const char *name, enum MAV_MISSION_TYPE &mtype)
+{
+    if (strcmp(name, "mission.dat") == 0) {
+        mtype = MAV_MISSION_TYPE_MISSION;
+        return true;
+    }
+    if (strcmp(name, "fence.dat") == 0) {
+        mtype = MAV_MISSION_TYPE_FENCE;
+        return true;
+    }
+    if (strcmp(name, "rally.dat") == 0) {
+        mtype = MAV_MISSION_TYPE_RALLY;
+        return true;
+    }
+    return false;
+}
+
+/*
+  get one item
+ */
+bool AP_Filesystem_Mission::get_item(uint32_t idx, enum MAV_MISSION_TYPE mtype, mavlink_mission_item_int_t &item)
+{
+    switch (mtype) {
+    case MAV_MISSION_TYPE_MISSION: {
+        auto *mission = AP::mission();
+        if (!mission) {
+            return false;
+        }
+        return mission->get_item(idx, item);
+    }
+    case MAV_MISSION_TYPE_FENCE:
+        return MissionItemProtocol_Fence::get_item_as_mission_item(idx, item);
+
+    case MAV_MISSION_TYPE_RALLY:
+        return MissionItemProtocol_Rally::get_item_as_mission_item(idx, item);
+
+    default:
+        break;
+    }
+    return false;
+}
+
+// get number of items
+uint32_t AP_Filesystem_Mission::get_num_items(enum MAV_MISSION_TYPE mtype) const
+{
+    switch (mtype) {
+    case MAV_MISSION_TYPE_MISSION: {
+        auto *mission = AP::mission();
+        if (!mission) {
+            return 0;
+        }
+        return mission->num_commands();
+    }
+        
+    case MAV_MISSION_TYPE_FENCE: {
+        auto *fence = AP::fence();
+        if (fence == nullptr) {
+            return 0;
+        }
+        return fence->polyfence().num_stored_items();
+    }
+
+    case MAV_MISSION_TYPE_RALLY: {
+        auto *rally = AP::rally();
+        if (rally == nullptr) {
+            return 0;
+        }
+        return rally->get_rally_total();
+    }
+        
+    default:
+        break;
+    }
+    return 0;
+}
diff --git a/libraries/AP_Filesystem/AP_Filesystem_Mission.h b/libraries/AP_Filesystem/AP_Filesystem_Mission.h
new file mode 100644
index 0000000000..aaa215a641
--- /dev/null
+++ b/libraries/AP_Filesystem/AP_Filesystem_Mission.h
@@ -0,0 +1,56 @@
+/*
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "AP_Filesystem_backend.h"
+#include <GCS_MAVLink/GCS_MAVLink.h>
+
+class AP_Filesystem_Mission : public AP_Filesystem_Backend
+{
+public:
+    // functions that closely match the equivalent posix calls
+    int open(const char *fname, int flags) override;
+    int close(int fd) override;
+    int32_t read(int fd, void *buf, uint32_t count) override;
+    int32_t lseek(int fd, int32_t offset, int whence) override;
+    int stat(const char *pathname, struct stat *stbuf) override;
+
+private:
+    // only allow up to 4 files at a time
+    static constexpr uint8_t max_open_file = 4;
+
+    // header at front of the file
+    struct header {
+        uint16_t magic = 0x763d;
+        uint16_t data_type; // MAV_MISSION_TYPE_*
+        uint32_t num_items;
+    };
+
+    struct rfile {
+        bool open;
+        uint32_t file_ofs;
+        uint32_t num_items;
+        enum MAV_MISSION_TYPE mtype;
+    } file[max_open_file];
+
+    bool check_file_name(const char *fname, enum MAV_MISSION_TYPE &mtype);
+
+    // get one item
+    bool get_item(uint32_t idx, enum MAV_MISSION_TYPE mtype, mavlink_mission_item_int_t &item);
+
+    // get number of items
+    uint32_t get_num_items(enum MAV_MISSION_TYPE mtype) const;
+};