diff --git a/changes/ticket15358 b/changes/ticket15358
new file mode 100644
index 0000000000..8c85d51007
--- /dev/null
+++ b/changes/ticket15358
@@ -0,0 +1,3 @@
+ o Features (control protocl):
+   - Support network-liveness GETINFO key and NETWORK_LIVENESS events in the
+     control protocol.  Resolves ticket #15358.
diff --git a/src/or/circuitstats.c b/src/or/circuitstats.c
index 7b3ad56537..3ced5afad5 100644
--- a/src/or/circuitstats.c
+++ b/src/or/circuitstats.c
@@ -1232,6 +1232,9 @@ circuit_build_times_network_is_live(circuit_build_times_t *cbt)
   }
   cbt->liveness.network_last_live = now;
   cbt->liveness.nonlive_timeouts = 0;
+
+  /* Tell control.c */
+  control_event_network_liveness_update(1);
 }
 
 /**
@@ -1316,6 +1319,9 @@ circuit_build_times_network_close(circuit_build_times_t *cbt,
                  "Tor has not observed any network activity for the past %d "
                  "seconds. Disabling circuit build timeout recording.",
                  (int)(now - cbt->liveness.network_last_live));
+
+      /* Tell control.c */
+      control_event_network_liveness_update(0);
     } else {
       log_info(LD_CIRC,
              "Got non-live timeout. Current count is: %d",
diff --git a/src/or/control.c b/src/or/control.c
index b8b29d7134..de24294efc 100644
--- a/src/or/control.c
+++ b/src/or/control.c
@@ -178,6 +178,9 @@ static int write_stream_target_to_buf(entry_connection_t *conn, char *buf,
 static void orconn_target_get_name(char *buf, size_t len,
                                    or_connection_t *conn);
 
+static int get_cached_network_liveness(void);
+static void set_cached_network_liveness(int liveness);
+
 /** Given a control event code for a message event, return the corresponding
  * log severity. */
 static INLINE int
@@ -958,6 +961,7 @@ static const struct control_event_t control_event_table[] = {
   { EVENT_TRANSPORT_LAUNCHED, "TRANSPORT_LAUNCHED" },
   { EVENT_HS_DESC, "HS_DESC" },
   { EVENT_HS_DESC_CONTENT, "HS_DESC_CONTENT" },
+  { EVENT_NETWORK_LIVENESS, "NETWORK_LIVENESS" },
   { 0, NULL },
 };
 
@@ -2205,6 +2209,24 @@ getinfo_helper_onions(control_connection_t *control_conn,
   return 0;
 }
 
+/** Implementation helper for GETINFO: answers queries about network
+ * liveness. */
+static int
+getinfo_helper_liveness(control_connection_t *control_conn,
+                      const char *question, char **answer,
+                      const char **errmsg)
+{
+  if (strcmp(question, "network-liveness") == 0) {
+    if (get_cached_network_liveness()) {
+      *answer = tor_strdup("up");
+    } else {
+      *answer = tor_strdup("down");
+    }
+  }
+
+  return 0;
+}
+
 /** Callback function for GETINFO: on a given control connection, try to
  * answer the question <b>q</b> and store the newly-allocated answer in
  * *<b>a</b>. If an internal error occurs, return -1 and optionally set
@@ -2289,6 +2311,8 @@ static const getinfo_item_t getinfo_items[] = {
          "Information about and from the ns consensus."),
   ITEM("network-status", dir,
        "Brief summary of router status (v1 directory format)"),
+  ITEM("network-liveness", liveness,
+       "Current opinion on whether the network is live"),
   ITEM("circuit-status", events, "List of current circuits originating here."),
   ITEM("stream-status", events,"List of current streams."),
   ITEM("orconn-status", events, "A list of current OR connections."),
@@ -5094,6 +5118,52 @@ control_event_or_authdir_new_descriptor(const char *action,
   return 0;
 }
 
+/** Cached liveness for network liveness events and GETINFO
+ */
+
+static int network_is_live = 0;
+
+static int
+get_cached_network_liveness(void)
+{
+  return network_is_live;
+}
+
+static void
+set_cached_network_liveness(int liveness)
+{
+  network_is_live = liveness;
+}
+
+/** The network liveness has changed; this is called from circuitstats.c
+ * whenever we receive a cell, or when timeout expires and we assume the
+ * network is down. */
+int
+control_event_network_liveness_update(int liveness)
+{
+  if (liveness > 0) {
+    if (get_cached_network_liveness() <= 0) {
+      /* Update cached liveness */
+      set_cached_network_liveness(1);
+      log_debug(LD_CONTROL, "Sending NETWORK_LIVENESS UP");
+      send_control_event_string(EVENT_NETWORK_LIVENESS, ALL_FORMATS,
+                                "650 NETWORK_LIVENESS UP\r\n");
+    }
+    /* else was already live, no-op */
+  } else {
+    if (get_cached_network_liveness() > 0) {
+      /* Update cached liveness */
+      set_cached_network_liveness(0);
+      log_debug(LD_CONTROL, "Sending NETWORK_LIVENESS DOWN");
+      send_control_event_string(EVENT_NETWORK_LIVENESS, ALL_FORMATS,
+                                "650 NETWORK_LIVENESS DOWN\r\n");
+    }
+    /* else was already dead, no-op */
+  }
+
+  return 0;
+}
+
 /** Helper function for NS-style events. Constructs and sends an event
  * of type <b>event</b> with string <b>event_string</b> out of the set of
  * networkstatuses <b>statuses</b>. Currently it is used for NS events
diff --git a/src/or/control.h b/src/or/control.h
index a9f2725878..2d02443834 100644
--- a/src/or/control.h
+++ b/src/or/control.h
@@ -67,6 +67,7 @@ int control_event_or_authdir_new_descriptor(const char *action,
                                             size_t desclen,
                                             const char *msg);
 int control_event_my_descriptor_changed(void);
+int control_event_network_liveness_update(int liveness);
 int control_event_networkstatus_changed(smartlist_t *statuses);
 
 int control_event_newconsensus(const networkstatus_t *consensus);
@@ -174,7 +175,8 @@ void control_free_all(void);
 #define EVENT_TRANSPORT_LAUNCHED      0x0020
 #define EVENT_HS_DESC                 0x0021
 #define EVENT_HS_DESC_CONTENT         0x0022
-#define EVENT_MAX_                    0x0022
+#define EVENT_NETWORK_LIVENESS        0x0023
+#define EVENT_MAX_                    0x0023
 
 /* sizeof(control_connection_t.event_mask) in bits, currently a uint64_t */
 #define EVENT_CAPACITY_               0x0040