Butyllithium may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis:
- n-Butyllithium, abbreviated BuLi or <sup>n</sup>BuLi
- sec-Butyllithium, abbreviated sec-BuLi or <sup>s</sup>BuLi, has 2 stereoisomers, but is commonly used as racemate
- tert-Butyllithium, abbreviated tert-BuLi or <sup>t</sup>BuLi
- Isobutyllithium