Actinide borohydrides, first discovered during the Manhattan Project, are broadly defined as complexes that form B–H–M bonds, where M is a 5f metal. The earliest examples were discovered during the search for volatile uranium complexes to separate fissile U-235 for atomic weapons. After World War II, it was reported that simple borohydride complexes such as U(BH₄)₄, U(BH₄)₃(BH₃Me), and U(BH₃Me)₄ were extremely volatile, setting into motion efforts to discover new actinide borohydride complexes and understand their exceptional properties. In this article, we provide a comprehensive review of the synthesis, properties, and structures of actinide complexes bearing the most common types of borohydride ligands, namely tetrahydroborates (BH₄⁻), methyltrihydroborates (BH₃Me⁻), and their Lewis base adducts. Thorium and uranium complexes containing the chelating borohydride ligand N,N-dimethylaminodiboranate (H₃BNMe₂BH₃⁻) and less-common hydroborate, dihydroborate, and trihydroborate complexes of the actinides are also discussed.