Adoor is a municipality in the Pathanamthitta district of Kerala, India. It is the headquarters of the Adoor Taluk and Adoor Revenue Division. Adoor is located 18 km (11.2 mi) southwest of the district headquarters Pathanamthitta and 85 km (52.8 mi) north of the state capital Thiruvananthapuram.

According to the 2011 Indian Census, Adoor had a population of 29,171.

"Adoor" (Ad-oor) in Malayalam is derived from two words: "Ad" meaning "separated" (adarnu) and "oor" meaning "place" or "land". Thus, it translates to "adarnu kittiya ooru" in Malayalam, which means "land obtained through separation" in English.

The "Ad" can be also interpreted as "Aadyan" (ആഢ്യൻ), making it "Aadyanmaarude Ooru" (ആഢ്യൻമാരുടെ ഊര്) in Malayalam meaning "Land of the Noble Personnel" in English.

The history of Adoor is directly connected to the history of Kollam district. During the 1st century A.D., most of the places in Kollam district were ruled by the Ay Kingdom, with their headquarters at south Travancore. It is known that during the rule of the Ay Kings, a Buddhist Monastery existed in Adoor. Some megalithic monuments like dolmens, dating back to the Neolithic period, have been discovered in the Enadimangalam village of Adoor Taluk.^{[citation needed]}

Adoor was once part of Ilayidathu Dynasty and Pandalam dynasty. In 1741, Venad Maharaja Marthandavarma included Adoor to the Travancore Kingdom. King Marthanda Varma once came to Adoor to hide from Ettuvettil Pillai (a wealthy family who tried to capture King Marthandavarma and to get hold of his throne) and sought the help from Chittundayil house but it was refused and then support and shelter was provided by the grandmother of Nellimuttil family at Adoor, in the later days, after he became the King he then made revenge to the Chittundayil house and granted help to the Nellimuttil house. During the rule of Dharmaraja, a notable event was the battle against Tippu Sultan, where travancore made alliance with the East India Company. During the rule of Rani Gowri Parvathy Bayi, in 1812 A.D., pandalam was annexed to the kingdom of Travancore. The Anantharamapuram market situated at Parakkode is known to be one of the oldest, largest and busiest market during the Travancore era. After India got its independence in 1947, the Maharaja of Travancore refused to join Indian Union, but later had to agree. On 1 July 1949, Travancore and Cochin States were integrated and the Maharaja of Travancore became Rajpramukh of Travancore-Cochin State. On 1 November 1956, The State of Kerala was formed integrating the earlier regions of Travancore, Cochin and Malabar. After that, Adoor was in Kollam district until a new 13th district called, the Pathanamthitta District came into existence as a separate administrative unit on the 1 November 1982. The newly formed Adoor Taluk comprised nine Villages of Kunnathur Taluk and two villages of Mavelikkara Taluk of former Kollam and Alappuzha districts. On 1 April 1990, Adoor municipality came into existence and the area under Adoor municipality is presently known as Adoor Town.^{[citation needed]}

Adoor was part of Central Travancore and was never directly under British rule. Adoor was a major town of both wealthy Hindu families and notable Saint Thomas Christian families. Adoor was never captured by King Marthanadavarma.

Adoor Dharma Hospital (now known as Adoor General Hospital) was established in the 1880s during Travancore rule.