diff --git a/ecs.hpp b/ecs.hpp
index 629fecd..8d27512 100644
--- a/ecs.hpp
+++ b/ecs.hpp
@@ -718,6 +718,8 @@ namespace ecs_hpp
         entity_id id_{0u};
     };
 
+    bool operator<(const entity& l, const entity& r) noexcept;
+
     bool operator==(const entity& l, const entity& r) noexcept;
     bool operator==(const entity& l, const const_entity& r) noexcept;
 
@@ -781,6 +783,8 @@ namespace ecs_hpp
         entity_id id_{0u};
     };
 
+    bool operator<(const const_entity& l, const const_entity& r) noexcept;
+
     bool operator==(const const_entity& l, const entity& r) noexcept;
     bool operator==(const const_entity& l, const const_entity& r) noexcept;
 
@@ -836,6 +840,9 @@ namespace ecs_hpp
         entity owner_;
     };
 
+    template < typename T >
+    bool operator<(const component<T>& l, const component<T>& r) noexcept;
+
     template < typename T >
     bool operator==(const component<T>& l, const component<T>& r) noexcept;
     template < typename T >
@@ -886,6 +893,9 @@ namespace ecs_hpp
         const_entity owner_;
     };
 
+    template < typename T >
+    bool operator<(const const_component<T>& l, const const_component<T>& r) noexcept;
+
     template < typename T >
     bool operator==(const const_component<T>& l, const component<T>& r) noexcept;
     template < typename T >
@@ -1218,6 +1228,11 @@ namespace ecs_hpp
         return detail::as_const(*owner_).find_components<Ts...>(id_);
     }
 
+    inline bool operator<(const entity& l, const entity& r) noexcept {
+        return (&l.owner() < &r.owner())
+            || (&l.owner() == &r.owner() && l.id() < r.id());
+    }
+
     inline bool operator==(const entity& l, const entity& r) noexcept {
         return &l.owner() == &r.owner()
             && l.id() == r.id();
@@ -1293,6 +1308,11 @@ namespace ecs_hpp
         return (*owner_).find_components<Ts...>(id_);
     }
 
+    inline bool operator<(const const_entity& l, const const_entity& r) noexcept {
+        return (&l.owner() < &r.owner())
+            || (&l.owner() == &r.owner() && l.id() < r.id());
+    }
+
     inline bool operator==(const const_entity& l, const entity& r) noexcept {
         return &l.owner() == &r.owner()
             && l.id() == r.id();
@@ -1371,6 +1391,11 @@ namespace ecs_hpp
         return detail::as_const(owner_).template find_component<T>();
     }
 
+    template < typename T >
+    bool operator<(const component<T>& l, const component<T>& r) noexcept {
+        return l.owner() < r.owner();
+    }
+
     template < typename T >
     bool operator==(const component<T>& l, const component<T>& r) noexcept {
         return l.owner() == r.owner();
@@ -1428,6 +1453,11 @@ namespace ecs_hpp
         return detail::as_const(owner_).template find_component<T>();
     }
 
+    template < typename T >
+    bool operator<(const const_component<T>& l, const const_component<T>& r) noexcept {
+        return l.owner() < r.owner();
+    }
+
     template < typename T >
     bool operator==(const const_component<T>& l, const component<T>& r) noexcept {
         return l.owner() == r.owner();