Isoprene is a volatile C5 hydrocarbon. It is produced by a wide variety of organisms and has been shown to play a role in protection of plants under abiotic stress conditions. It also has many different uses as an industrial chemical: most notably as a precursor for synthetic rubbers, but also for production of elastomers, copolymers, adhesives, and specialised chemicals. Modifying and/or engineering isoprene production in plants has the potential to contribute to engineered stress resistance. Moreover, as petrochemical sources of isoprene increase in price and become more scarce, bioproduction routes through microbial processes are becoming more attractive. Here we examine biotechnological aspects of isoprene production and review the current state of the art for both microbial-based industrial bioprocesses and plant engineering.