Three subspecies of modern rhinos have tragically become extinct due to different threats.

Western Black Rhino (Diceros bicornis longipes): It was declared extinct in 2011 by IUCN. The primary reason for its extinction was rampant poaching for its valuable horn. Loss of habitat due to human encroachment and conflict with humans also contributed to its decline.
Northern White Rhino (Ceratotherium simum cottoni): The last male of this subspecies died in 2018, leaving only two surviving females, making it functionally extinct. Poaching for their horns decimated their population.
Vietnamese Javan Rhino (Rhinoceros sondaicus annamiticus) became extinct in 2011. The primary cause of its extinction was also poaching for its rhino horn, driven by the demand for traditional medicine and illegal wildlife trade. This subspecies was restricted to the Cat Tien National Park in Vietnam, making it one of the world's rarest and most critically endangered mammals.