Hey! I seen a thread. Someone was asking where certain Pokémon are in the game. I know all the locations of all Legendary Pokemon in the game and I thought it was be beneficial to post them here.

Here's a list of all Pokémon locations.

Before collecting all 8 gym badges:

Baby Lugia

-Obtained through game event

Lugia

-Evolved from Baby Lugia (through happiness)

Suicune

-North Cave at Snowsoft city
-Only at Low Tide (time-based)
-HM Surf, Strength required

Ho-oh

-Sea Path
-Require HM Surf, Dive
-Dive spot directly below the twin swimmer trainers
-After dived, go up then left, then resurface
-Cavern with "Rainbow Wing" sign

Kyogre

-Hydro Cave at Morient Town
-Go due east from town gym
-Navigate south through trees
-May require HM Flash (but not necessary since route very easy to travel)

Groudon

-Obtained through game event at Cave of Origins
-May require HM Flash

The elementary birds (Zapdos, Articuno, Moltres)

-In their respective element Isles surrounding Cinnabar Isle
-Require HM Surf

Entei

-Obtained through game event at Fire Cave, outside Morient Town

Before Elite Four (E4) battle, require all 8 badges:

Shaymin

-Require HM Surf
-Surf up north from Veronica Town

Raikou and Registeel

-Electric Cave at east of Veronica Town
-Require HM Surf

Regirock

-Francia Cave (Go through entrance at Pina Francia, not entrance in forest)

Regice

-Lost Cave at west of Luster Town
-Require HM Surf, Waterfall and Flash

Mewtwo

-Above Waterfall of Blue Path
-Require HM SUrf, Waterfall

Deoxys

-Raleso Town (Meteor Crash Site) which is south of Sand Path

Regigigas

-Center of Ring Path
-Require HM Surf, Waterfall

Rayquaza

-Cave in the desert near Sand Path

Manaphy

-Lost Sea (require some searching through caverns)
-Require HM Surf, Waterfall

Phione

-Same as Manaphy
-Except that after obtaining Manaphy, DO NOT PRESS START AND/OR FLY
AWAY AFTER RECEIVING THE EGG!!! (Unless you want to go through the
treacherous path again). Instead, run all the way below from the
spot where you receive the egg to face Phione

After E4 Battle:

Dark Lugia

-Obtained through game event at northwest of Vermillion City

After E4 battle and completing DL event at Vermillion City 

Cresselia

-Renica Tunnel (area above Blackglasses guy)
-Require HM Surf

Heatran

-Fire Cave outside Morient Town, go up narrow path near female trainer

Darkrai

-Lost Cave which is west of Luster Town (path to ladder that leads to area where
Regice formerly resides)
-Require HM Surf, Waterfall, Flash

Dialga

-Lost Lorina at Lost Cave (go through door formerly blocked by Regice)
-Require HM Surf, Waterfall, Flash
(For the legendary pixie trios (Uxie, Azelf, Mesprit), u have to activate them by seeing them
upon entering Lost Lorina. Only then would they appear at their respective locations:

Uxie

-Ancient Cave (along narrow path in a small cave section)

Azelf

-Unown Cave (along narrow path west of cave)  

Mesprit

-Thin Forest

Latios

-Must have watched TV when at home after E4 battle
-Moving around routes in Gento, have to manually search

Latias

-Must have watched TV when at home after E4 battle
-S.F.Path (just walk through it)

Giratina

-The hole in the ground at Blue Path Cave
-Require HM Surf, Waterfall

Palkia

-Cave at Mount Blaze which is east of Borora Town

Arceus

-Below Ring Path
-Require HM Surf, Waterfall

Celebi

-Exit ofBug Forest to Sky Path, near Rotom house
-May require HM Cut

Jirachi

-Rock south of Tabuli Town

Mew

-Below Jirachi rock, near Lost Sea entrance
-Require HM Surf

Angeallen

-Cave at Rentelbud City

Hope this Helped!

dude registeel isn't in the electric cave i've searched for hours

ShadowLugia4911 : Have you tried the Power Plant?

i have tried the powerplant but never mind i used cheats to find one in the wild

Wow this is amazing dude you literally listed all the obtainable legendaires I was thinking about replaying this game as well this should help me refresh my memory of their locations.

austipokedude : Hey, man. No problem I'll be posting more locations of legendary Pokemon in different games shortly. If you have any particular game you want to request, I will find the legendaries in it and post them in a new tread (:

Awesome, Dean! I have never played this game, maybe I will try it to get baby lugia and others. Nice one! 10/10

Awesome man!
I guess you will be doing walkthrough mostly on vizzed.
Nice walkthroughs by the way!

nice! this will be really useful because i was gonna play this game.thanks!