diff --git a/src/overmap.cpp b/src/overmap.cpp
index 79c745e2e6322..ee87163bd84ad 100644
--- a/src/overmap.cpp
+++ b/src/overmap.cpp
@@ -4062,6 +4062,9 @@ bool overmap::can_place_special( const overmap_special &special, const tripoint_
     if( !special.id ) {
         return false;
     }
+    if( special.flags.count( "UNIQUE" ) > 0 && overmap_buffer.contains_unique_special( special.id ) ) {
+        return false;
+    }
 
     return std::all_of( special.terrains.begin(),
     special.terrains.end(), [&]( const overmap_special_terrain & elem ) {
@@ -4097,6 +4100,9 @@ void overmap::place_special(
     if( !force ) {
         cata_assert( can_place_special( special, p, dir, must_be_unexplored ) );
     }
+    if( special.flags.count( "UNIQUE" ) > 0 ) {
+        overmap_buffer.add_unique_special( special.id );
+    }
 
     const bool blob = special.flags.count( "BLOB" ) > 0;
 
@@ -4256,10 +4262,11 @@ void overmap::place_specials( overmap_special_batch &enabled_specials )
         }
 
         if( iter->special_details->flags.count( "UNIQUE" ) > 0 ) {
+            const overmap_special_id &id = iter->special_details->id;
             const int min = iter->special_details->occurrences.min;
             const int max = iter->special_details->occurrences.max;
 
-            if( x_in_y( min, max ) ) {
+            if( !overmap_buffer.contains_unique_special( id ) && x_in_y( min, max ) ) {
                 // Min and max are overloaded to be the chance of occurrence,
                 // so reset instances placed to one short of max so we don't place several.
                 iter->instances_placed = max - 1;
diff --git a/src/overmapbuffer.cpp b/src/overmapbuffer.cpp
index e021bbc878cb9..4495be3984c72 100644
--- a/src/overmapbuffer.cpp
+++ b/src/overmapbuffer.cpp
@@ -205,6 +205,7 @@ void overmapbuffer::clear()
 {
     overmaps.clear();
     known_non_existing.clear();
+    placed_unique_specials.clear();
     last_requested_overmap = nullptr;
 }
 
@@ -883,6 +884,19 @@ bool overmapbuffer::check_overmap_special_type( const overmap_special_id &id,
     return om_loc.om->check_overmap_special_type( id, om_loc.local );
 }
 
+void overmapbuffer::add_unique_special( const overmap_special_id &id )
+{
+    if( contains_unique_special( id ) ) {
+        debugmsg( "Unique overmap special placed more than once: %s", id.str() );
+    }
+    placed_unique_specials.emplace( id );
+}
+
+bool overmapbuffer::contains_unique_special( const overmap_special_id &id ) const
+{
+    return placed_unique_specials.find( id ) != placed_unique_specials.end();
+}
+
 static omt_find_params assign_params(
     const std::string &type, int const radius, bool must_be_seen,
     ot_match_type match_type, bool existing_overmaps_only,
diff --git a/src/overmapbuffer.h b/src/overmapbuffer.h
index 95ab2ca641b1e..58ff215946a32 100644
--- a/src/overmapbuffer.h
+++ b/src/overmapbuffer.h
@@ -491,6 +491,8 @@ class overmapbuffer
         mutable std::set<point_abs_om> known_non_existing;
         // Cached result of previous call to overmapbuffer::get_existing
         overmap mutable *last_requested_overmap;
+        // Set of globally unique overmap specials that have already been placed
+        std::unordered_set<overmap_special_id> placed_unique_specials;
 
         /**
          * Get a list of notes in the (loaded) overmaps.
@@ -524,6 +526,15 @@ class overmapbuffer
                                 const tripoint_abs_omt &loc );
         bool check_overmap_special_type_existing( const overmap_special_id &id,
                 const tripoint_abs_omt &loc );
+
+        /**
+         * Adds the given globally unique overmap special to the list of placed specials.
+         */
+        void add_unique_special( const overmap_special_id &id );
+        /**
+         * Returns true if the given globally unique overmap special has already been placed.
+         */
+        bool contains_unique_special( const overmap_special_id &id ) const;
     private:
         /**
          * Go thorough the monster groups of the overmap and move out-of-bounds