Jón Gnarr Kristinsson is an Icelandic actor, comedian, and politician who became the Mayor of Iceland's capital city Reykjavík on 15 June 2010, and stepped down on 16 June 2014. Born Jón Gunnar Kristinsson, Jón legally changed his middle name in 2005 to the way his mother pronounced it when he was a boy. He is married to Jóhanna Jóhannsdóttir with whom he has five children. His daughter, Margret, is a fitness model and IFBB competitor.

Jón Gnarr suffered from dyslexia and had learning difficulties as a child. Jón Gnarr recounts these experiences in his book The Indian, an autobiographical account of his childhood. Jón Gnarr has been diagnosed with ADHD and has actively discussed his life with ADHD publicly.

Jón was known as Jónsi Punk as a teenager and played bass in a punk band called Nefrennsli ("Runny Nose"). He attended a number of high schools,but didn't complete the university entrance exam. During the 1980s Jón and his future wife, Jóhanna Jóhannsdóttir, became acquainted with the members of the band the Sugarcubes, including Björk and Einar Örn Benediktsson. Björk remained a close friend to Jóhanna, while Einar would become an important political ally to Jón.

In 1994, Jón teamed up with Sigurjón Kjartansson to form the radio duo Tvíhöfði. In 1997, he joined TV station Stöð 2 where he wrote and starred in several seasons of the Icelandic comedy show Fóstbræður. His best known movies are The Icelandic Dream and A Man like Me. His stand-up comedy show Ég var einu sinni nörd (I Used To Be a Nerd) is autobiographical.

In late 2009 Jón formed the Best Party with a number of others with no background in politics, including Einar. The Best Party, a satirical political party that parodies Icelandic politics and aims to make the life of the citizens more fun, managed a plurality in the 2010 municipal elections in Reykjavík, with the party gaining six out of 15 seats on the City Council. Einar, second on the party's list behind Jón, won a seat on the council.

Jón ended up defeating the Independence Party-led municipal government of Hanna Birna Kristjánsdóttir. His victory is widely seen as a backlash against establishment politicians in the wake of Iceland's 2008-2011 financial crisis.

Jón's political platform included promises of "free towels in all swimming pools, a polar bear for the Reykjavík zoo, all kinds of things for weaklings, Disneyland in the Vatnsmýri area," etc.

Upon being elected, Jón announced that he would not enter a coalition government with anyone that had not watched "The Wire", eventually entering a coalition with the Social Democratic Alliance (Samfylkingin) as its junior partner to govern Reykjavík.

As mayor, Jón has been a source of amusement and shock. He also protested the Chinese government's treatment of human rights activist Liu Xiaobo. He has stated that the importance of the EU is highly over-rated. On October 30, 2013, Jón Gnarr announced that he would not seek a second term in office when his first term expired in June 2014.

Since leaving office, Gnarr has campaigned for Iceland to abandon its laws requiring citizens to have traditional Icelandic names. Gnarr also authored a book entitled Gnarr!: How I Became the Mayor of a Large City in Iceland and Changed the World.