Marine macroalgae (seaweeds) consist of a diverse range of species with diverse morphology and bioactive properties. The potential for genetic improvement to increase the value of the production of such molecules and other economically important traits is likely to be high as procedures for cultivation of many species are well established, genetic diversity is often high, sexual propagation is often possible and seaweeds generally have a short generation time that allows rapid transition from one selected generation to the next. The need for genetic improvement has been voiced by industry for many years. Despite this, there is little published research describing seaweed genetic improvement methodology, results or impact. This review draws on knowledge from other groups of species and describes options, benefits and knowledge needed for the genetic improvement of macroalgae. In conclusion, the review highlights how a well-designed genetic improvement program, which targets one or a few select economically valuable traits whilst limiting inbreeding, could provide potentially large benefits for industries reliant on the culture of seaweeds. Progress will, to a large extent, rely on the magnitude of genetic variation for the trait in question.