Isidoro Díaz Mejía (born 14 February 1938) is a Mexican former professional footballer who played as a midfielder.

Isidoro Díaz played most of his club career for Guadalajara, where he won 15 titles, including 7 league titles and the first ever edition of the CONCACAF Champions' Cup in 1962.

He represented Mexico in three World Cups (1962, 1966 and 1970). He made 68 appearances for the Mexico national team between 1960 and 1970.^[1]

Guadalajara

• CONCACAF Champions' Cup: 1962
• Mexican Primera División: 1956–57, 1958–59, 1959–60, 1960–61, 1961–62 1963–64, 1965–1966
• Mexican Champions Cup: 1956–57, 1958–59, 1959–60, 1960–61, 1963–64, 1964–65
• Mexican Cup: 1963