Thiago Moura Monteiro (Brazilian Portuguese: [tʃiˈaɡu mõˈtejɾu]; born 31 May 1994) is a Brazilian professional tennis player.

Monteiro has a career-high ATP singles ranking of world No. 61 achieved on 17 October 2022. He also has a career-high ATP doubles ranking of No. 144, achieved on 31 January 2022. He is currently the No. 2 Brazilian tennis player.

On the ITF Junior Circuit, Monteiro peaked in the rankings at No. 2 on 2 February 2012, with his biggest junior singles title being the Grade A, Copa Gerdau in Porto Alegre, Brazil, in 2011.

In his first ATP match, as a wildcard ranked world No. 338 in the ATP 500 Rio de Janeiro in February 2016, Monteiro upset No. 9 Jo-Wilfried Tsonga in the first round. In the second round, Monteiro lost to eventual champion Pablo Cuevas. In his next tournament, the ATP 250 São Paulo, Monteiro won two matches (against former World No. 9 Nicolás Almagro, and Daniel Muñoz de la Nava), losing again to eventual champion Cuevas in the quarterfinals.

On May 8, 2016, Monteiro won his first ATP Challenger title in Aix-en-Provence, France. He defeated Carlos Berlocq in the final.