Corbyn was born in idyllic Wiltshire in 1949. His parents were peace campaigners who met during the 1936 Spanish Civil War.
He's been a left-winger for most of his life. While still at school he became active in his local Labour party as well as the League Against Cruel Sports.
He was first elected as Member of Parliament for Islington North in 1983 and has been reelected seven times. Most recently in 2015 he gained 60.24% of the vote and a majority of 21,194 votes.
In 1984, Corbyn invited two convicted IRA terrorists to London to publicise prison abuses just two weeks after the IRA killed five people in an explosion in Brighton in an attempt to kill Margaret Thatcher.
He is vigorously anti-war. Corbyn opposed the 1982 Falklands War and both Gulf Wars. He has advocated for the UK to leave NATO.
He strongly opposed apartheid and was one of eight politicians arrested in 1984 for breaking a ban on protests outside South Africa's embassy in London.
He is the most rebellious Labour MP on record. Corbyn has defied the party 500 times since 2001, voting against proposals on terrorism, ID cards, and immigration.
In 1999, his marriage to Claudia Bracchitta broke up over a dispute on where to send their son to school. Corbyn wanted to send him to an inner-city state school, Bracchitta disagreed.
Corbyn has worked for Press TV, the English-language, Iranian-owned television station. He's also referred to members of Hezbollah and Hamas as "friends."
When the scandal over MP expenses broke in 2010, it didn't touch Corbyn. He claims the least amount of expenses of all elected MPs, with the rent for his office costing around £14,000.
He was a staunch supporter of former Venezuelan president Hugo Chavez, publishing a blog called "Thank you Mr. Chavez" when the South American leader died in 2013.
If you thought to put £10 on him winning the leadership fight in June, you'd be £1,000 richer on Monday. Corbyn was a 100-1 outsider before the campaign began.