Klefki locations — where to catch

In Lumiose City (Legends: Z-A)

• Lumiose Sewers — Walk, Static Encounter
• Wild Zone 17 — Walk
• Wild Zone 20 — Walk

In Paldea (Scarlet & Violet)

• Glaseado Mountain — Walk
• South Province (Area Six) — Walk

Other games (5)

• Sword / Shield — The Isle of Armor (Gen 8): Fields of Honor, Max Lair
• Ultra Sun / Ultra Moon (Gen 7): Thrifty Megamart
• Sun / Moon (Gen 7): Poke Pelago, Thrifty Megamart
• Omega Ruby / Alpha Sapphire (Gen 6): Route 113
• X / Y (Gen 6): Friend Safari, Kalos Route 15, Kalos Route 16, Lost Hotel

Klefki — full Pokédex entry