Mati Kaal (born 3 June 1946) is an Estonian zoologist, mammalogist, animal ecologist and former zoo director. He worked at Tallinn Zoo from 1968 and served as its director from 1975 until his retirement in 2016. He is known for research on Estonia's large carnivores, for popularising zoology and nature conservation, and for his long association with conservation work involving the European mink. He is one of the founders of the Estonian Nature Fund.
Kaal was born in Tallinn and spent much of his childhood in Mui village in Pöide Parish on Saaremaa, where he began school and lived for about fourteen years. He later studied in Tallinn and graduated from Tallinn Secondary School No. 2 in 1964. He studied biology at the University of Tartu, graduating in 1969.
Before completing university, Kaal joined Tallinn Zoo in 1968 during his required practical placement. After the death of director Károly Stern in 1975, Kaal became the zoo's director at the age of 29. During his tenure, the zoo completed its long-planned move from Kadriorg to the larger Veskimetsa site in 1983.
Under Kaal's directorship, Tallinn Zoo became the first zoo in the Soviet Union to join the World Association of Zoos and Aquariums (WAZA) in 1989, and the institution later became active in regional and international zoo associations. In 2013, Kaal announced that he intended to step down after the completion of the zoo's environmental education centre. He left the directorship at the end of June 2016 and retired from the post after more than four decades of service to the zoo. WAZA later listed him as a director emeritus of Tallinn Zoo.
Kaal's research has focused on Estonia's large carnivores, especially the brown bear, wolf and lynx. His early scholarly work included a 1976 study of the brown bear in Estonia published in Bears: Their Biology and Management.
Kaal was one of the founders of the Estonian Nature Fund in 1991. He also chaired the board of the Lutreola Foundation, an organisation devoted to the conservation of the European mink. During Kaal's directorship, Tallinn Zoo developed into an important centre for the conservation of the European mink. A later scientific review identified Tallinn Zoo's 1984 conservation-breeding programme as the first such programme for the species, while Estonian reporting on Kaal's 2016 conservation award linked him to the zoo's species-conservation work and to reintroduction methods used on Hiiumaa.
Beyond his research and zoo work, Kaal has been a prominent public populariser of zoology and nature conservation. The University of Tartu Narva College has described him as a promoter of natural science and environmental protection, the author and translator of popular-science writing, and a participant in the development of Estonian specialist terminology. After retirement, he also worked as a nature guide for safari visitors in Tanzania; in 2024 he published the travel and nature book Minu sõbrad Serengetis.
Kaal received the Order of the White Star, III class, in 2001. In 2014 he received the Tallinn Coat of Arms for his long service and dedication as director of Tallinn Zoo. In 2016 he was awarded the Eerik Kumari Nature Conservation Award. In 2020 he was named an honorary citizen of Harju County. WAZA's 2019 annual report listed him among the association's honorary members.