2001-2008: Sits in the House of Commons representing the constituency of Henley.
During his tenure, Johnson twice serves as the Conservative spokesman on business, innovation and skills while the party is out of government.
2008-2016: Serves as London mayor.
May 7, 2015: Returns to the House of Commons representing the constituency of Uxbridge and South Ruislip.
2016: Co-leader of the campaign to take Britain out of the European Union. This put Johnson in opposition to then-Prime Minister David Cameron, a fellow Conservative, who resigned after voters approved Brexit in a national referendum on June 23, 2016.
2016-2018: Serves as Foreign Secretary, which makes him one of the most senior members of Prime Minister Theresa May's Cabinet. Johnson resigned in July 2018 in opposition to May's strategy for a ``soft'' Brexit that would maintain close ties with the EU.
June 7, 2019: Theresa May resigns as Conservative Party leader over her failure to persuade Parliament to back the Brexit agreement she negotiated with the EU.
The party is split between those who back May and hard-liners, led by Johnson, who are willing to risk a no-deal Brexit in order to wring concessions from the EU.
July 23, 2019: Johnson is elected Conservative Party leader in a vote of party members. He formally takes office as prime minister the next day, inheriting a minority government that relies on votes from Northern Ireland's Democratic Unionist Party to pass legislation.
Johnson insists Britain will leave the EU on Oct. 31, with or without a deal.
Aug. 28, 2019: Announces he will shut down Parliament until mid-October, giving opponents less time to thwart a no-deal Brexit.
Sept. 3, 2019: Twenty-one rebel Conservative Party lawmakers support legislation requiring the government to seek an extension of Brexit negotiations if it can't negotiate an agreement with the EU.
The measure passes and the rebels are expelled from the party.
Sept. 5, 2019: Johnson asserts he would rather be ``dead in a ditch'' than ask the EU for another extension.
Sept. 24, 2019: U.K. Supreme Court rules government's suspension of Parliament was unlawful.
Oct. 19, 2019: Johnson asks the EU to delay Brexit again. The new deadline is Jan. 31.
Nov. 6, 2019: Parliament is dissolved and early elections are set for mid-December as Johnson seeks a mandate for his Brexit strategy.
Dec. 12, 2019: Johnson wins an 80-seat majority in the general election, giving him the backing to push through Brexit legislation.
Jan. 23, 2020: The Brexit deal becomes law after approval by the U.K. Parliament. The European Parliament approves the deal six days later.
March 23, 2020: Johnson places U.K. in first lockdown due to COVID-19.
April 5, 2020: Johnson was hospitalized and later moved to intensive care with COVID-19.
He was released from the hospital on April 12, thanking the nurses who sat with him through the night to make sure he kept breathing.
Nov. 3, 2021: The government orders Conservative lawmakers to support a change in ethics rules to delay the suspension of Johnson supporter Owen Paterson, who had been censured for breaching lobbying rules. The measure passes.
Nov. 4, 2021: Facing an angry backlash from lawmakers of all parties, Johnson reverses course and allows lawmakers to vote on Paterson's suspension. Paterson resigns.
Nov. 30, 2021: British media begin reporting allegations that government officials attended parties in government offices during November and December 2020 in violation of COVID-19 lockdown rules.
The scandal grows over the coming weeks, ultimately including reports of more than a dozen parties. Johnson maintains that there were no parties and no rules were broken, but opposition leaders criticize the government for breaking the law as others sacrificed to combat the pandemic.
Dec. 8, 2021: Johnson authorizes an investigation into the ``Partygate'' scandal. Pressure builds for a leadership challenge, but fizzles.
March 23, 2022: The government announces a mid-year spending plan that is criticized for doing too little to help people struggling with the soaring cost of living.
Treasury chief Rishi Sunak refuses to delay a planned income tax increase or impose a windfall profits tax on oil and gas companies benefiting from rising energy prices.
April 9, 2022: Johnson meets Ukrainian President Volodymyr Zelenskyy in Kyiv, pledging a new package of military and economic support. The move helps bolster Johnson and his supporters, who argue that the government should be focused on the crisis in Ukraine and other major issues, not domestic political squabbles.
April 12, 2022: Johnson is fined 50 pounds ($63) for attending one of the parties. Johnson apologizes.
Opposition parties characterize him as the first U.K. prime minister in history who has been shown to have broken the law while in office.
May 13, 2022: Unionists in Northern Ireland block the government over Brexit trade rules.
May 18, 2022: Office for National Statistics releases data showing annual inflation accelerated to 9% in April, the highest in 40 years. The report fuels calls for the government to do more to combat a cost-of-living crisis fueled by soaring energy costs.
May 22, 2022: Findings of the Partygate investigation are published. It provides information on 16 gatherings at the Downing Street complex that houses the prime minister's home and office and other government offices between May 2020 and April 2021.
The report details instances of excessive drinking, property damage and disrespect to cleaners and security staff.
May 25, 2022: Johnson says he was ``vindicated'' by the Partygate investigation. Speaking to lawmakers, Johnson said he ``briefly'' attended some of the gatherings to thank departing staff members for their work but he had no knowledge of the excesses that occurred after he left.
May 26, 2022: Government reverses course on its tax decision on oil and gas companies and announces plans for a 25% windfall profits levy.
June 3, 2022: Johnson roundly booed as he walks up the steps of St. Paul's cathedral to attend a service of thanksgiving for Queen Elizabeth II during celebrations for her Platinum Jubilee, in what critics suggest is a defining moment that demonstrates his wavering support from the public.
June 6, 2022: Johnson wins a confidence vote but some 41% of his party vote against him, placing his future leadership in doubt.