The Assumption Cathedral (Thai: อาสนวิหารอัสสัมชัญ) is the principal Catholic church of Thailand, located at 23 Oriental Avenue, New Road, in the Bang Rak District of Bangkok.

[1] Throughout the latter half of the 19th century, the church and surrounding area played an important role for Christian missionaries arriving in Bangkok, particularly after 1860.

[1] The church has a relatively tall rectangular structure with a red brick exterior which stands out against its surrounding white buildings.

Construction costs were largely covered by a local catholic businessman, Mr Low Khiok Chiang (also known as Jacobe) who owned the nearby Kiam Hoa Heng & Company, a Chinese Teochew family business.

For weekday, including Saturday, the mass is celebrated at 6am in the chapel located on the south side of the cathedral, in the area of Assumptionsuksa School.

The significant part of the cathedral is in the crypt underneath the Sanctuary, which kept the remains of the bishops and the missionaries, including that of Fr Nicholas Boonkerd Kitbamrung, who was proclaimed a martyr by Pope John Paul II on 5 March 2000 in the Vatican.

Besides being a place of worship and for performing sacred ceremonies, the role of the Assumption Cathedral is the church of the head of the local diocese, which as of 2014[update] was led by Cardinal Michael Meechai Kitboonchu.