diff --git a/data/scripts/maps/Route101.inc b/data/scripts/maps/Route101.inc
index 6840c45f4b..aa15933377 100644
--- a/data/scripts/maps/Route101.inc
+++ b/data/scripts/maps/Route101.inc
@@ -204,6 +204,7 @@ Route101_Movement_14EA58:: @ 814EA58
 
 Route101_EventScript_14EA64:: @ 814EA64
 	msgbox Route101_Text_16D25E, 2
+	setflag FLAG_SET_SHINY_MON
 	end
 
 Route101_EventScript_14EA6D:: @ 814EA6D
diff --git a/include/constants/flags.h b/include/constants/flags.h
index a8067f6cab..a96c6afcc8 100644
--- a/include/constants/flags.h
+++ b/include/constants/flags.h
@@ -880,6 +880,8 @@
 
 #define FLAG_LANDMARK_BERRY_MASTERS_HOUSE (SYSTEM_FLAGS + 0x63)
 
+#define FLAG_SET_SHINY_MON (SYSTEM_FLAGS + 0x64)
+
 
 // Daily Flags. These 64 flags are cleared once per day.
 #define DAILY_FLAGS_START (SYSTEM_FLAGS + 0xC0)
diff --git a/include/pokemon.h b/include/pokemon.h
index 169045c0ca..c95299bfce 100644
--- a/include/pokemon.h
+++ b/include/pokemon.h
@@ -623,6 +623,7 @@ bool8 IsPokeSpriteNotFlipped(u16);
 u8 GetLevelUpMovesBySpecies(u16, u16 *);
 u8 TryIncrementMonLevel(struct Pokemon *);
 bool8 IsShiny(struct Pokemon *mon);
+bool8 IsShinyOtIdPersonality(u32 otId, u32 personality);
 void RandomlyGivePartyPokerus(struct Pokemon *party);
 void PartySpreadPokerus(struct Pokemon *party);
 
diff --git a/src/pokemon_1.c b/src/pokemon_1.c
index a23bb33245..a4dc05777e 100644
--- a/src/pokemon_1.c
+++ b/src/pokemon_1.c
@@ -1,9 +1,11 @@
 #include "global.h"
 #include "data2.h"
 #include "constants/abilities.h"
+#include "constants/flags.h"
 #include "constants/items.h"
 #include "constants/moves.h"
 #include "constants/species.h"
+#include "event_data.h"
 #include "main.h"
 #include "pokemon.h"
 #include "random.h"
@@ -82,6 +84,8 @@ const s8 gNatureStatTable[][5] =
 #include "data/pokemon/evolution.h"
 #include "data/pokemon/level_up_learnset_pointers.h"
 
+static u32 ForceShinyPersonality(u32 personality);
+
 void ZeroBoxMonData(struct BoxPokemon *boxMon)
 {
     u8 *raw = (u8 *)boxMon;
@@ -239,12 +243,46 @@ void CreateMonWithNature(struct Pokemon *mon, u16 species, u8 level, u8 fixedIV,
     do
     {
         personality = Random32();
+        if (FlagGet(FLAG_SET_SHINY_MON))
+        {
+            personality = ForceShinyPersonality(personality);
+        }
     }
     while (nature != GetNatureFromPersonality(personality));
 
     CreateMon(mon, species, level, fixedIV, 1, personality, 0, 0);
 }
 
+static u32 ForceShinyPersonality(u32 personality)
+{
+    int currentBit;
+    u32 playerOT = gSaveBlock2.playerTrainerId[0]
+                | (gSaveBlock2.playerTrainerId[1] << 8)
+                | (gSaveBlock2.playerTrainerId[2] << 16)
+                | (gSaveBlock2.playerTrainerId[3] << 24);
+    u16 otVal = (playerOT >> 16) ^ (playerOT & 0xFFFF);
+
+    u16 bitSelector = Random();
+    u16 personalityVal = (personality >> 16) ^ (personality & 0xFFFF);
+    for (currentBit = 3; currentBit < 16; currentBit++)
+    {
+        int shiftedBit = 1 << currentBit;
+        int otBitSet = (otVal & shiftedBit) != 0;
+        int personalityBitSet = (personalityVal & shiftedBit) != 0;
+        if (otBitSet + personalityBitSet == 1)
+        {
+            // Bits are different, so let's arbitrarily flip one of them such
+            // that the XOR of the folded OT and personality values will be 0.
+            if (bitSelector & shiftedBit)
+                personality ^= shiftedBit;
+            else
+                personality ^= (shiftedBit << 16);
+        }
+    }
+
+    return personality;
+}
+
 void CreateMonWithGenderNatureLetter(struct Pokemon *mon, u16 species, u8 level, u8 fixedIV, u8 gender, u8 nature, u8 unownLetter)
 {
     u32 personality;
diff --git a/src/wild_encounter.c b/src/wild_encounter.c
index 19778e29b6..73657b767a 100644
--- a/src/wild_encounter.c
+++ b/src/wild_encounter.c
@@ -3982,6 +3982,7 @@ static void CreateWildMon(u16 species, u8 b)
 {
     ZeroEnemyPartyMons();
     CreateMonWithNature(&gEnemyParty[0], species, b, 0x20, PickWildMonNature());
+    FlagClear(FLAG_SET_SHINY_MON);
 }
 
 static bool8 GenerateWildMon(const struct WildPokemonInfo *wildMonInfo, u8 area, bool8 checkRepel)