diff --git a/distribution/changelog.txt b/distribution/changelog.txt
index 385c30cbbd..28d8dba81b 100644
--- a/distribution/changelog.txt
+++ b/distribution/changelog.txt
@@ -1,6 +1,7 @@
 0.4.15 (in development)
 ------------------------------------------------------------------------
 - Feature: [#15642] Track design placement can now use contruction modifier keys (ctrl/shift).
+- Feature: [#21521] [Plugin] Add hook 'park.guest.softcap.calculate' called before calculating the soft guest cap.
 - Change: [#22596] Land ownership fixes described by .parkpatch files are now only considered on scenarios.
 - Fix: [#2614] The colour tab of the ride window does not hide invisible cars (original bug).
 - Fix: [#15406] Tunnels on steep Side-Friction track are drawn too low.
diff --git a/distribution/openrct2.d.ts b/distribution/openrct2.d.ts
index f5f0767173..1011d849a0 100644
--- a/distribution/openrct2.d.ts
+++ b/distribution/openrct2.d.ts
@@ -515,6 +515,7 @@ declare global {
         subscribe(hook: "network.chat", callback: (e: NetworkChatEventArgs) => void): IDisposable;
         subscribe(hook: "network.join", callback: (e: NetworkEventArgs) => void): IDisposable;
         subscribe(hook: "network.leave", callback: (e: NetworkEventArgs) => void): IDisposable;
+        subscribe(hook: "park.guest.softcap.calculate", callback: (e: ParkCalculateGuestCapArgs) => void): IDisposable;
         subscribe(hook: "ride.ratings.calculate", callback: (e: RideRatingsCalculateArgs) => void): IDisposable;
         subscribe(hook: "vehicle.crash", callback: (e: VehicleCrashArgs) => void): IDisposable;
 
@@ -640,6 +641,7 @@ declare global {
         "network.chat" |
         "network.join" |
         "network.leave" |
+        "park.guest.softcap.calculate" |
         "ride.ratings.calculate" |
         "vehicle.crash";
 
@@ -1415,6 +1417,14 @@ declare global {
         readonly crashIntoType: VehicleCrashIntoType;
     }
 
+    /**
+     * The 'suggestedGuestMaximum' field in this interface can be used to override
+     * the park's suggested guest cap.
+     */
+    interface ParkCalculateGuestCapArgs {
+        suggestedGuestMaximum: number;
+    }
+
     /**
      * APIs for the in-game date.
      */
diff --git a/src/openrct2/scripting/HookEngine.cpp b/src/openrct2/scripting/HookEngine.cpp
index a86f538730..77ead25f9b 100644
--- a/src/openrct2/scripting/HookEngine.cpp
+++ b/src/openrct2/scripting/HookEngine.cpp
@@ -34,6 +34,7 @@ static const EnumMap<HOOK_TYPE> HooksLookupTable({
     { "map.change", HOOK_TYPE::MAP_CHANGE },
     { "map.changed", HOOK_TYPE::MAP_CHANGED },
     { "map.save", HOOK_TYPE::MAP_SAVE },
+    { "park.guest.softcap.calculate", HOOK_TYPE::PARK_CALCULATE_GUEST_CAP },
 });
 
 HOOK_TYPE OpenRCT2::Scripting::GetHookType(const std::string& name)
diff --git a/src/openrct2/scripting/HookEngine.h b/src/openrct2/scripting/HookEngine.h
index 3b78481f25..839691aedb 100644
--- a/src/openrct2/scripting/HookEngine.h
+++ b/src/openrct2/scripting/HookEngine.h
@@ -42,6 +42,7 @@ namespace OpenRCT2::Scripting
         MAP_CHANGE,
         MAP_CHANGED,
         MAP_SAVE,
+        PARK_CALCULATE_GUEST_CAP,
         COUNT,
         UNDEFINED = -1,
     };
diff --git a/src/openrct2/scripting/ScriptEngine.h b/src/openrct2/scripting/ScriptEngine.h
index c5f8d41d83..12cc0d24a8 100644
--- a/src/openrct2/scripting/ScriptEngine.h
+++ b/src/openrct2/scripting/ScriptEngine.h
@@ -46,7 +46,7 @@ namespace OpenRCT2
 
 namespace OpenRCT2::Scripting
 {
-    static constexpr int32_t OPENRCT2_PLUGIN_API_VERSION = 98;
+    static constexpr int32_t OPENRCT2_PLUGIN_API_VERSION = 99;
 
     // Versions marking breaking changes.
     static constexpr int32_t API_VERSION_33_PEEP_DEPRECATION = 33;
diff --git a/src/openrct2/world/Park.cpp b/src/openrct2/world/Park.cpp
index 15c48d3a35..8065b78e1c 100644
--- a/src/openrct2/world/Park.cpp
+++ b/src/openrct2/world/Park.cpp
@@ -33,6 +33,7 @@
 #include "../ride/RideData.h"
 #include "../ride/ShopItem.h"
 #include "../scenario/Scenario.h"
+#include "../scripting/ScriptEngine.h"
 #include "../util/Util.h"
 #include "../windows/Intent.h"
 #include "Entrance.h"
@@ -43,6 +44,7 @@
 #include <type_traits>
 
 using namespace OpenRCT2;
+using namespace OpenRCT2::Scripting;
 
 namespace OpenRCT2::Park
 {
@@ -157,6 +159,21 @@ namespace OpenRCT2::Park
         }
 
         suggestedMaxGuests = std::min<uint32_t>(suggestedMaxGuests, 65535);
+
+#ifdef ENABLE_SCRIPTING
+        auto& hookEngine = GetContext()->GetScriptEngine().GetHookEngine();
+        if (hookEngine.HasSubscriptions(HOOK_TYPE::PARK_CALCULATE_GUEST_CAP))
+        {
+            auto ctx = GetContext()->GetScriptEngine().GetContext();
+            auto obj = DukObject(ctx);
+            obj.Set("suggestedGuestMaximum", suggestedMaxGuests);
+            auto e = obj.Take();
+            hookEngine.Call(HOOK_TYPE::PARK_CALCULATE_GUEST_CAP, e, true);
+
+            suggestedMaxGuests = AsOrDefault(e["suggestedGuestMaximum"], static_cast<int32_t>(suggestedMaxGuests));
+            suggestedMaxGuests = std::clamp<uint16_t>(suggestedMaxGuests, 0, UINT16_MAX);
+        }
+#endif
         return suggestedMaxGuests;
     }