Organic-inorganic　metal　halide　perovskites　(most　notably　CH3NH3PbI3)　have　demonstrated　remarkable　physical　attributes　for　photovoltaic　and　diverse　optoelectronic　applications,　whereas　concerns　about　toxicity　owing　to　the　use　of　lead　in　the　chemical　composition　still　motivate　further　exploration　of　new,　nontoxic　candidates.　Lead-free　halide　double　perovskites　(HDPs),　designed　by　the　rational　chemical　substitution　of　Pb(2+)with　other　nontoxic　candidate　elements,　have　recently　attracted　interest　as　a　fascinating　alternative　to　their　Pb-based　counterparts.　Herein,　recent　advances　in　crystal　structures,　physical　properties,　and　versatile　optoelectronic　applications　of　lead-free　HDPs,　such　as　solar　cells,　photodetectors,　X-ray　detectors,　and　light-emitting　diodes,　are　reviewed.　Perspectives　to　improve　the　physical　and　photoelectric　properties　of　existing　HDP　materials　are　also　discussed　and　will　favor　future　development　of　new,　lead-free　HDP　candidates.