Peter Thomson OF (born 1948) is a Fijian diplomat and the United Nations Secretary-General's Special Envoy for the Ocean, and President of the United Nations General Assembly from September 2016 until September 2017. He served as Fiji's Permanent Representative to the United Nations February 2010 to August 2017, with concurrent duties as Fiji's Ambassador to Cuba.

In his capacity as Fiji's Permanent Representative to the UN, in 2014, Thomson served as president of the Executive Board of the United Nations Development Programme, the United Nations Population Fund and the United Nations Office of Project Services. In the same capacity, in 2013, he took responsibility for Fiji's Chairmanship of the Group of 77 and China, the UN's largest negotiating group, made up of 133 developing countries. In 2011, he was elected as president of the 17th Session of the Assembly of the International Seabed Authority (ISA), and in 2015 was elected as president of 21st Session of the ISA Council.

During his time as Fiji's Permanent Representative to the United Nations, Thomson was the prime-mover of the name-change of the UN's Regional Group from that of "the Asian Group" to its new name of "the Asia-Pacific Group", effective 2011. In 2014, the President of Fiji conferred on Thomson the award of Officer of the Order of Fiji.

Peter Thomson, a fifth generation Fijian, was born to British colonial administrator Sir Ian Thomson (Colonial Secretary in the 1960s and later as Governor of the British Virgin Islands) and his wife Lady Nancy Thomson. He married publisher Marijcke Thomson in Fiji in 1973. They have two children, James and Nicola, and four granddaughters.

Educated at Suva Grammar School and Natabua High School, he finished schooling at the International Centre, Sevenoaks School, England, in 1967. He later obtained a BA in political studies at Auckland University and a postgraduate diploma in development studies at Wolfson College, Cambridge.

Thomson began work as a Fijian civil servant in 1972, working in rural development and local government as District Officer in the districts of Navua, Macuata and Taveuni. In 1978, he was posted to Fiji's Ministry of Foreign Affairs. He was seconded in 1979 to the Pacific Islands Forum Secretariat, before being posted to Japan in 1980 as Chargé d'Affaires, entrusted with the task of establishing Fiji's Embassy in Tokyo. He served in Tokyo until 1984, when he was appointed Fiji's Consul General in Sydney, Australia. Returning to Fiji in 1986, he served as the Government's Permanent Secretary of Information, and was a member of the boards of the Fiji Visitors Bureau, Fiji TV and the Fiji Broadcasting Commission.

In 1987, he served at Fiji's Government House as Permanent Secretary to Governor-General Ratu Sir Penaia Ganilau. During this time between the two coups d'état of 1987, the Governor-General was the sole executive authority of Fiji. After the September 1987 coup d'état, he "found himself a target as the high-profile white permanent secretary to Fiji's governor-general, embroiled in a constitutional crisis and with indigenous supremacists demanding his head". As a result, he was gaoled by the Fijian Army for four days, and subsequently emigrated to New Zealand, then Australia.

From 1988 onwards, he worked as an investment and management consultant on Pacific Island affairs for various government agencies, regional organisations, universities and investment corporations. In 1990, the East–West Center published his diagnostic study "Trade and Investment in the Pacific Islands." His New Zealand-registered company, Thomson Pacific, managed Mitsubishi Trust Bank's real estate assets in Auckland. During this time he was a founding director and shareholder of Tabua Investments Ltd, one of the prime developers of Fiji's premier tourism resort Denarau Island Resort, and was a principal in the construction of the Sheraton Villas project at Denarau. He was a founder member of the executive committees of the Australia-Fiji Business Council, and is a founder and life-member of the New Zealand-Fiji Business Council.