Martti Oiva Kalevi Ahtisaari (23 June 1937 – 16 October 2023) was a Finnish politician and diplomat who was the president of Finland from 1994 to 2000. He was Finland's Ambassador to Tanzania from 1973 to 1977 and United Nations Commissioner for Namibia from 1977 to 1981. Noted for his international peace work, he received the Nobel Peace Prize in 2008.

Ahtisaari was a United Nations special envoy for Kosovo, charged with organizing the Kosovo status process negotiations. These negotiations aimed to resolve a long-running dispute in Kosovo, which later declared its independence from Serbia in 2008. In October 2008, he was awarded the Nobel Peace Prize "for his important efforts, on several continents and over more than three decades, to resolve international conflicts". The Nobel statement said that Ahtisaari had played a prominent role in resolving serious and long-lasting conflicts, including ones in Namibia, Aceh (Indonesia), Kosovo and Serbia, and Iraq.

Martti Ahtisaari was born in Viipuri, Finland (now Vyborg, Russia) on 23 June 1937. His father, Oiva Ahtisaari, whose grandfather Julius Marenius Adolfsen had emigrated with his parents to Kotka, Finland in 1872 from Tistedalen in Southern Norway, took Finnish citizenship in 1929 and Finnicized his surname from Adolfsen in 1935. Oiva was working as a NCO in the supply troops in Viipuri when Martti was born.

The Continuation War (World War II) took Oiva Ahtisaari to the front as a non-commissioned officer army mechanic, while Martti's mother, Tyyne, moved to Kuopio with her son to escape immediate danger from the war in 1940. Kuopio was where Ahtisaari spent most of his childhood, eventually attending Kuopion Lyseo high school.

In 1952, Martti Ahtisaari moved to Oulu with his family. There he continued his education in high school, graduating in 1956. He also joined the local YMCA. After completing his military service (Ahtisaari held the rank of captain in the Finnish Army Reserve), he began to study at Oulu teachers' college, attending the two-year course which enabled him to qualify as a primary-school teacher in 1959.

In the summer of 1960, Ahtisaari signed the contract for the position of director of the Swedish Agency for International Development physical education boarding school in Karachi, Pakistan, after interviewing in Sweden and hearing about the offer announced by the YMCA in April of that year. There, he also trained as a teacher.

He returned to Finland in 1963 and began his studies in the Helsinki School of Economics and soon became the Executive Director of the Helsinki International Student Club and Student International Aid, where he made friends with Namibian Nickey Iyambo. He also joined the international students' organisation AIESEC. In 1965, he joined the Ministry for Foreign Affairs in its Bureau for International Development Aid, to set up the International Development Assistance Office together with Jaakko Iloniemi, which was a pioneering office, as the Finnish presence in international cooperation in the Third World was non-existent. Ahtisaari remained in that office until 1972, where he served from 1971 as assistant to the director, a position he combined with his presence on the Government's Advisory Committee for Trade and Industry Affairs of Developing Countries.

Ahtisaari began his diplomatic career in 1973 when he became Finland's Ambassador to Tanzania, Zambia, Somalia and Mozambique, an office he held until 1977. This new mission allowed him to get closer to East African affairs, monitoring from Dar es Salaam the independence process of Namibia and maintaining close contacts with South West Africa People's Organisation (SWAPO). In 1977 he was recalled by the United Nations to succeed Seán MacBride as United Nations Commissioner for Namibia, a post he held until 1981, and as representative of Secretary-General Kurt Waldheim from 1978.