diff --git a/changelog.md b/changelog.md
index b342b6e7..f0c23113 100644
--- a/changelog.md
+++ b/changelog.md
@@ -15,6 +15,7 @@ These changes will (most likely) be included in the next version.
 - Entities outside of the arena can no longer target players, pets, or monsters inside of the arena.
 - Tab completion for `/ma kick` and `/ma restore` now uses actual player names instead of display names.
 - If the world of an exit warp, leaderboard, or linked class chest is not available on (re)load, MobArena now throws a config error instead of failing silently later down the road.
+- Overlapping arena regions are now reported as warnings in the server log during arena load, because overlapping regions can result in undefined, buggy behavior.
 - MobArena's internal version checker has been rewritten. It now uses the resource API of Spigot instead of DBO. It's also a lot more lightweight and caches results for up to one hour.
 
 ## [0.104] - 2019-08-08
diff --git a/src/main/java/com/garbagemule/MobArena/ArenaMasterImpl.java b/src/main/java/com/garbagemule/MobArena/ArenaMasterImpl.java
index 6ab23fae..dfa9d05a 100644
--- a/src/main/java/com/garbagemule/MobArena/ArenaMasterImpl.java
+++ b/src/main/java/com/garbagemule/MobArena/ArenaMasterImpl.java
@@ -532,6 +532,8 @@ public void loadArenasInWorld(String worldName) {
         if (arenaNames == null || arenaNames.isEmpty()) {
             return;
         }
+
+        List<Arena> arenas = new ArrayList<>();
         for (String arenaName : arenaNames) {
             Arena arena = getArenaWithName(arenaName);
             if (arena != null) continue;
@@ -539,7 +541,31 @@ public void loadArenasInWorld(String worldName) {
             String arenaWorld = config.getString("arenas." + arenaName + ".settings.world", "");
             if (!arenaWorld.equals(worldName)) continue;
 
-            loadArena(arenaName);
+            Arena loaded = loadArena(arenaName);
+            if (loaded != null) {
+                arenas.add(loaded);
+            }
+        }
+
+        reportOverlappingRegions(arenas);
+    }
+
+    private void reportOverlappingRegions(List<Arena> arenas) {
+        // If we iterate the upper/lower triangular matrix of the cartesian
+        // product of the arena list, we avoid not only duplicate reports like
+        // "a vs. b and b vs. a", but also "self comparisons" (j = i + 1).
+        for (int i = 0; i < arenas.size(); i++) {
+            Arena a = arenas.get(i);
+            for (int j = i + 1; j < arenas.size(); j++) {
+                Arena b = arenas.get(j);
+                if (a.getRegion().intersects(b.getRegion())) {
+                    plugin.getLogger().warning(String.format(
+                        "Regions of arenas '%s' and '%s' overlap!",
+                        a.configName(),
+                        b.configName()
+                    ));
+                }
+            }
         }
     }
 
diff --git a/src/main/java/com/garbagemule/MobArena/region/ArenaRegion.java b/src/main/java/com/garbagemule/MobArena/region/ArenaRegion.java
index c4af962e..d9462c59 100644
--- a/src/main/java/com/garbagemule/MobArena/region/ArenaRegion.java
+++ b/src/main/java/com/garbagemule/MobArena/region/ArenaRegion.java
@@ -242,6 +242,23 @@ public boolean contains(Location l, int radius) {
                 (y + radius >= p1.getBlockY() && y - radius <= p2.getBlockY()));
     }
 
+    public boolean intersects(ArenaRegion other) {
+        if (lobbySetup && other.lobbySetup) {
+            if (intersects(l1, l2, other.l1, other.l2)) {
+                return true;
+            }
+        }
+        return intersects(p1, p2, other.p1, other.p2);
+    }
+
+    private boolean intersects(Location a1, Location a2, Location b1, Location b2) {
+        return (
+            b1.getBlockX() <= a2.getBlockX() && a1.getBlockX() <= b2.getBlockX() &&
+            b1.getBlockZ() <= a2.getBlockZ() && a1.getBlockZ() <= b2.getBlockZ() &&
+            b1.getBlockY() <= a2.getBlockY() && a1.getBlockY() <= b2.getBlockY()
+        );
+    }
+
     // Region expand
     public void expandUp(int amount) {
         int x = p2.getBlockX();