Wikipedia mentions that the term was used in Oxford and Cambridge universities at least in 1464.
But I wonder whether the title was used somewhere before. Was is used under Ancient Rome?
From the Online Etymology Dictionary entry the Latin is given as praesidentum (nominative praesidens) meaning "president, governor", from whence English derived it via the Old French "president".
The OED lists several usages dating from the 1370's and 1380's for both the appointed head of a territory or district (sense 1) and for the appointed or elected head of a committee or group who then presides over meetings (sense 2).
The 1374 entry in the OED (sense 1) is the oldest I saw there.