Thalassery (Malayalam: [t̪ɐlɐʃ(ː)eːɾi] ), formerly Tellicherry (colonial name), is a commercial city and municipality on the Malabar Coast in Kannur district in the state of Kerala, India, bordered by the districts of Mahe and Kozhikode. Thalassery municipality has a population of just under 100,000 as of 2011 census. Thalassery Heritage City has an area of 23.98 square kilometres (9.26 sq mi). Thalassery has an altitude ranging from 2.5 to 30 metres (8 ft 2 in to 98 ft 5 in) above mean sea-level. It is located 25 km (15 mi) from Vadakara, 15 km (10 mi) from Mahé and 22 km (13 mi) from Kannur.

Tellicherry municipality was formed on 1 November 1866 according to the Madras Act 10 of 1865 (Amendment of the Improvements in City act 1850) of the British Indian Empire, making it the second oldest municipality in the state. At that time, the municipality was known as Tellicherry Commission and Tellicherry was the capital of North Malabar. G. M. Ballard, the Malabar collector, was the first president of the municipal commission. A European barrister, A. F. Lamaral, would later become the first Chairman of Thalassery municipality. Thalassery grew into a prominent place during European rule, due to its strategic geographic location. Thalassery has played a significant historical, cultural, educational and commercial role in the history of India, especially during the colonial period. On 9 February 2014, Thalassery taluk was split in two and Iritty taluk was formed. The northeastern hilly region of the former Thalassery Taluk, including Peravoor, Aralam, Ayyankunnu, Kottiyoor, and Kelakam, are within the Iritty Taluk area.