Quagsire locations — where to catch

In Kitakami (Scarlet & Violet – The Teal Mask)

• Chilling Waterhead — Walk
• Fellhorn Gorge — Walk
• Kitakami Wilds — Walk
• Mossfell Confluence — Walk
• Oni Mountain — Walk
• Timeless Woods — Static Encounter

In Sinnoh (Diamond, Pearl & Platinum)

• Great Marsh — Surf, Walk
• Route 212 — Surf, Walk

In Johto & Kanto (HeartGold & SoulSilver)

• Cliff Cave — Walk
• Cliff Edge Gate — Surf
• Johto Safari Zone — Surf, Walk
• Mt. Silver — Walk
• Mt. Silver Cave — Walk
• Route 10 — Walk
• Route 12 — Surf
• Route 13 — Surf, Walk
• Route 14 — Walk
• Route 15 — Walk
• Route 26 — Walk
• Route 27 — Walk
• Route 32 — Surf
• Route 47 — Surf, Walk
• Ruins of Alph — Surf
• Union Cave — Surf

In Hoenn (Ruby, Sapphire & Emerald)

• Safari Zone — Surf

In Johto & Kanto (Gold, Silver & Crystal)

• Mt. Silver — Walk
• Mt. Silver Cave — Walk
• Route 10 — Walk
• Route 12 — Surf
• Route 13 — Surf, Walk
• Route 14 — Walk
• Route 15 — Walk
• Route 26 — Walk
• Route 27 — Walk
• Route 32 — Surf
• Ruins of Alph — Surf, Walk
• Union Cave — Surf, Walk

Other games (7)

• Brilliant Diamond / Shining Pearl (Gen 8): Great Marsh, Route 212
• Sword / Shield — The Isle of Armor (Gen 8): Max Lair, Soothing Wetlands
• Sword / Shield (Gen 8): Dusty Bowl, Giant's Cap, Giant's Seat, Lake of Outrage, Rolling Fields, West Lake Axewell
• Ultra Sun / Ultra Moon (Gen 7): Ultra Space Wilds
• X / Y (Gen 6): Friend Safari, Kalos Route 14, Kalos Route 19
• Black 2 / White 2 (Gen 5): Route 8
• Colosseum (Gen 3): Pyrite Town

Quagsire — full Pokédex entry