The Congregation of Marian Fathers of the Immaculate Conception of the Most Blessed Virgin Mary is a fraternal community of consecrated life in the Roman Catholic Church. In America, the members of the Congregation are perhaps best known for their work promoting the message of Divine Mercy from Stockbridge, Massachusetts. They are also known for their devotion to Mary Immaculate, dedication to praying for the poor souls in Purgatory, and active service to the Church.

Founded in Poland in 1673 by St. Stanislaus Papczynski, today the Marian Congregation has well over 500 priests and brothers who labor in 19 countries: the USA, Argentina, Australia, Belarus, Brazil, Cameroon, Czech Republic, Germany, Italy, Kazakhstan, Latvia, Lithuania, Philippines, Poland, Portugal, Rwanda, Slovakia, Ukraine, and the United Kingdom.

The Marian Congregation is unique in that it has not only a founder, St. Stanislaus, but also what the Marians call a "Renovator": Lithuanian-born Blessed George Matulaitis.

Blessed George is credited with saving the Marian Congregation from annihilation when he renovated and refounded it in 1910. Prior to the Renovation, the Marian Congregation had been reduced to just one member due to relentless persecution by Russian authorities. With the support of the Pope and bishops, Blessed George rewrote the Marians' Constitutions, gathered new members, and unleashed the renovated Marian Congregation as a zealous army for Christ and the Church in the modern world.