The Archdiocese of Mercedes-Luján (Spanish: Arquidiócesis Mercedes-Luján; Latin: Archidioecesis Mercedensis-Luianensis) is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church in north-central Buenos Aires Province, Argentina.

Its mother church is the Catedral Basílica de Mercedes-Luján in Mercedes.

On 4 March 2019, Pope Francis raised it to a metropolitan archdiocese, with three suffragan dioceses within its ecclesiastical province.

Francis also appointed the first metropolitan archbishop, Jorge Eduardo Scheinig, who had been titular bishop of Ita.

[1] The archdiocese serves fifteen partidos in Buenos Aires Province: