Tuvshinbayar Naidan ( born 1 June 1984) is a Mongolian former professional judoka. He is the 2008 Olympic Champion, 2012 Olympic silver medalist, 2014 Asian games champion, 2017 World Championships bronze medalist, 2016 Asian Championships gold medalist, 2007 silver medalist and two-time (2008, 2011) bronze medalist in 100 kg division. Naidan is serving a sixteen-year jail term since 2021 for killing fellow judoka and childhood friend Erdenebileg Enkhbat.
At the 2006 Asian Games he finished in joint fifth place in both the heavyweight (100 kg) division and the open weight division.
Tuvshinbayar won the men's 100 kg division's gold medal at the 2008 Olympic Games in Beijing. He was the first Mongolian ever to win a gold medal at the Olympics, by defeating Kazakhstani judoka Askhat Zhitkeyev a sode tsurikomi goshi with the leg grab (according to the old rules of judo, where it is allowed to double and single leg takedowns, with the legs grabbed by the hands, similar to a freestyle wrestling). On 14 August 2008, he was inducted as the state honoured athlete of Mongolia as well as a hero of labour.
At the 2012 Summer Olympics in London, Tuvshinbayar won a silver medal, becoming the first Olympic multimedalist from Mongolia. He won his silver medal despite suffering a serious injury in the semifinal bout. Also, at the 2017 World Championships, he won a bronze medal match against Guram Tushishwili from Georgia by earning an ippon after a series of techniques including a kata gatame roll and an yoko shiho gatame, becoming both an Olympics and World Championships multimedalist.
In April 2021, Tüvshinbayar was jailed for 20 days following a drunken assault on Erdenebileg Enkhbat, who was a childhood friend. Enkhbat died on 24 December 2021 from a brain injury related to the assault. Following Enkhbat's death, new charges were filed against Tüvshinbayar. On 9 June 2022, the Khan-Uul District Court sentenced Tuvshinbayar to 16 years in prison for the deadly assault.