| João de Souza Mendes | |
| Birthname: | João de Souza Mendes Júnior |
| Country: | Portugal Brazil |
| Birth Date: | 1892 6, df=y |
| Birth Place: | Angra do Heroísmo, Portugal |
| Death Place: | Rio de Janeiro, Brazil |
João de Souza Mendes Júnior (23 June[1] 1892 – 10 July 1969) was a seven-time Brazilian chess champion and physician. Prior to emergence of Henrique Mecking, he was Brazil's most accomplished (given the span of his dominance) chess player.
Born in the Azores, Portugal, Souza Mendes played in the Brazilian Chess Championship 29 times, winning in 1927 (the first year the tournament was held), 1928, 1929, 1930, 1943, 1954, and 1958. He finished second five times, the last time in 1965 at age 73 when thirteen-year-old Henrique Mecking won, and took third five times.
He played for Brazil in Chess Olympiads at Buenos Aires 1939 and Helsinki 1952.
Souza Mendes died in Rio de Janeiro.