The Roman Catholic Diocese of San Nicolás de los Arroyos is based in the city of San Nicolás de los Arroyos, which is usually shortened to San Nicolás, and is a suffragan of the archdiocese of Rosario, Argentina.

[1][2] The diocesan seat, the Cathedral of St Nicholas of Myra, was home to a neglected statue of Our Lady of the Rosary that had been blessed by Pope Leo XIII.

The statue was rediscovered after an image of Our Lady appeared in a vision to a local lay woman mother-of-two Gladys Motta, leading to a renewed devotion under the title Our Lady of the Rosary of San Nicolás and the erection of a new Sanctuary with hostel for pilgrims and a center for promoting popular piety.

[3] In a decree signed on May 22, 2016 and made public a few days later, Héctor Cardelli, Bishop of the Diocese of San Nicolás, declared that the apparitions that occurred over a number of years beginning in the 1980s were supernatural in origin.

The devotion is thus approved "worthy of belief" at the Diocesan level within the Catholic Church.