The 1940 All-Ireland Minor Football Championship was the 12th staging of the All-Ireland Minor Football Championship, the Gaelic Athletic Association's premier inter-county Gaelic football tournament for boys under the age of 18.
Roscommon entered the championship as defending champions, however, they were defeated in the Connacht Championship.
On 22 September 1940, Louth won the championship following a 5âÂÂ05 to 2âÂÂ07 defeat of Mayo in the All-Ireland final. They led by 3âÂÂ01 to 1âÂÂ05 at half-time. This was Louth's second All-Ireland title and their first in four championship seasons.