Pokémon evolutions by trading

This is a list of Pokémon that evolve by trading. The classic four evolutions (Alakazam, Machoke, Graveler and Gengar) from Red/Blue/Yellow evolve only by trading, while most Pokémon from later generations require an item to be held in addition.

This information applies to any games that feature both Pokémon from the chain, so for example in Generation 1 the evolution chain with Steelix doesn't exist.