丁烯是四个化学式为C₄H₈的异构体的总称，它们主要是无色气体，来源是从原油提炼。这四个异构体都含有四个碳原子和一个双键。下表中列出了它们的IUPAC命名与常用名：

1-丁烯

顺-2-丁烯

反-2-丁烯

2-甲基丙烯

Butene, also known as butylene, is an alkene with the formula C₄H₈. It is a colourless gas that is present in crude oil as a minor constituent in quantities that are too small for viable extraction. It is therefore obtained by catalytic cracking of long chain hydrocarbons left during refining of crude oil. Cracking produces a mixture of products, and the butene is extracted from this by fractional distillation.