The Roman Catholic Diocese of Kottar (Latin: Kottaren(sis), Tamil: கோட்டாறு மறைமாவட்டம்) is a Latin Rite suffragan diocese in the ecclesiastical province of, Kottar, Kanyakumari District, southern India[1] yet depends on the missionary Roman Congregation for the Evangelization of Peoples Its episcopal see is Cathedral of St. Francis Xavier at Kottar in the town of Nagercoil, Tamil Nadu.

It was built by St. Francis Xavier in 1544 AD, rebuilt in 1603 over the small chapel original chapel, expanded in both 1713 and 1806.

[2] The Kottar parish was a constituent of Malabar Vicariate since 1657 AD and came under Roman Catholic Archdiocese of Verapoly.

[3] Again it became the southern center of Diocese of Quilon at its erection in 1853 AD.

[citation needed] (all Roman Rite natives) [6] As per 2017, it pastorally serves 307,104 Catholics on 750 km2 in 95 parishes with 243 priests (208 diocesan, 35 religious), 480 lay religious (35 brothers, 445 sisters) and 42 seminarians.