Rayappan Antony Muthu (1912–1980) was the third Bishop of the Roman Catholic Diocese of Vellore in Tamil Nadu, India from 1971 up to his death.

In addition, the Taluks of Thiruvannamalai and Chengam in the District of North Arcot, up to then belonging to the Archdiocese of Pondicherry-Cuddalore, were detached from it and added to the Diocese of Vellore.

He established Perpetual Adoration Monastery of Sisters of Poor Clare at Rangapuram, Sathuvachary as well erecting 17 new parishes.

A Mother and Child welfare programme was organized with the help of Catholic Relief Services.

During Muthu's period as Bishop, by a decision dated 20 January 1975, of the Sacred Congregation for the Evangelization of Peoples, the five taluks of the civil district of Chittoor, namely Chittoor, Palmaner, Kuppam, Bangaupalam and Satyavedu belonging to the Diocese of Vellore were detached from it and added to the Diocese of Nellore, Andhra Pradesh.