diff --git a/src/env.cpp b/src/env.cpp
index 09c4f8305..84a229636 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -297,7 +297,8 @@ bool string_set_contains(const T &set, const wchar_t *val) {
 /// Check if a variable may not be set using the set command.
 static bool is_read_only(const wchar_t *val) {
     const string_set_t env_read_only = {L"PWD", L"SHLVL", L"history", L"status", L"version", L"fish_pid", L"hostname", L"_"};
-    return string_set_contains(env_read_only, val);
+    return string_set_contains(env_read_only, val) ||
+        (in_private_mode() && wcscmp(L"fish_history", val) == 0);
 }
 
 static bool is_read_only(const wcstring &val) { return is_read_only(val.c_str()); }
diff --git a/src/fish.cpp b/src/fish.cpp
index 1746aed50..1d85c6eb3 100644
--- a/src/fish.cpp
+++ b/src/fish.cpp
@@ -218,7 +218,7 @@ int run_command_list(std::vector<std::string> *cmds, const io_chain_t &io) {
 
 /// Parse the argument list, return the index of the first non-flag arguments.
 static int fish_parse_opt(int argc, char **argv, fish_cmd_opts_t *opts) {
-    static const char * const short_opts = "+hilnvc:C:p:d:f:D:";
+    static const char * const short_opts = "+hPilnvc:C:p:d:f:D:";
     static const struct option long_opts[] = {{"command", required_argument, NULL, 'c'},
                                               {"init-command", required_argument, NULL, 'C'},
                                               {"features", required_argument, NULL, 'f'},
@@ -228,6 +228,7 @@ static int fish_parse_opt(int argc, char **argv, fish_cmd_opts_t *opts) {
                                               {"login", no_argument, NULL, 'l'},
                                               {"no-execute", no_argument, NULL, 'n'},
                                               {"profile", required_argument, NULL, 'p'},
+                                              {"private", no_argument, NULL, 'P'},
                                               {"help", no_argument, NULL, 'h'},
                                               {"version", no_argument, NULL, 'v'},
                                               {NULL, 0, NULL, 0}};
@@ -283,6 +284,10 @@ static int fish_parse_opt(int argc, char **argv, fish_cmd_opts_t *opts) {
                 g_profiling_active = true;
                 break;
             }
+            case 'P': {
+                start_private_mode();
+                break;
+            }
             case 'v': {
                 fwprintf(stdout, _(L"%s, version %s\n"), PACKAGE_NAME, get_fish_version());
                 exit(0);
diff --git a/src/history.cpp b/src/history.cpp
index eca9fa638..81240feab 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -1986,3 +1986,14 @@ void history_t::resolve_pending() {
     scoped_lock locker(lock);
     this->has_pending_item = false;
 }
+
+
+static bool private_mode = false;
+void start_private_mode() {
+    private_mode = true;
+    env_set_one(L"fish_history", ENV_GLOBAL, L"");
+}
+
+bool in_private_mode() {
+    return private_mode;
+}
diff --git a/src/history.h b/src/history.h
index b221f99ec..08e6f36c4 100644
--- a/src/history.h
+++ b/src/history.h
@@ -367,4 +367,9 @@ path_list_t valid_paths(const path_list_t &paths, const wcstring &working_direct
 /// return true if all paths in the list are valid
 /// Returns true for if paths is empty
 bool all_paths_are_valid(const path_list_t &paths, const wcstring &working_directory);
+
+/// Sets private mode on. Once in private mode, it cannot be turned off.
+void start_private_mode();
+/// Queries private mode status.
+bool in_private_mode();
 #endif