The Apostolic Vicariate of Phnom Penh (Khmer: សាវកជំនួសរាជធានីភ្នំពេញ) is a territorial subdivision of the Catholic Church in Cambodia.

Since 1860 it was responsible for the provinces Phsar Dek, Châu Đốc and Sóc Trăng of lower Cambodia, now part of Vietnam.

In 1989, the new constitution of Cambodia allowed freedom of religion once again, although the preaching of Christianity was still forbidden by the Council of Ministers.

In March 1990, the Cambodian government gave its approval for a group of Catholics to celebrate Easter Sunday, the first public worship in Cambodia in 15 years.

On 1 May 2015 the Cambodian Catholic Church opened an official diocesan inquiry for the martyrs in Tangkok, Kampong Thom Province, where Bishop Joseph Chhmar Salas died during the Khmer Rouge regime in 1977.