Lammy takes charge at a time of two global conflicts and has pledged to maintain continued support for Ukraine in its conflict against Russia and press for a ceasefire in the fighting in the Gaza Strip.
Reeves, 45, a former Bank of England economist, spent her time serving in opposition mending relations with the business community that were strained under former Labour leader Jeremy Corbyn, and pitching to voters that the party could be trusted with their money.
Starmer also picked John Healey as defence minister while Yvette Cooper becomes interior minister, known as home secretary, overseeing domestic security and policing.
Prime Minister Keir Starmer has nominated Rachel Reeves to become Chancellor of the Exchequer. (AP PHOTO)
Starmer has promised voters he will deliver change and provide political stability after 14 years of Conservative government which featured five prime ministers and an even higher turnover of other key ministers, including 10 education secretaries.
The appointments of his most senior team were widely expected, with ministers being named to the policy briefs they held while serving in opposition.
Angela Rayner will serve as deputy prime minister as well as secretary for levelling up, housing and communities.
Wes Streeting was named health minister, taking charge of a portfolio that will oversee the UK's struggling National Health Service (NHS), one of the biggest issues on voters' minds ahead of the election.
Ed Miliband, previously a Labour Party leader, was appointed energy security and net zero minister while Jonathan Reynolds becomes the new business minister.
Shabana Mahmood was named as justice minister while Bridget Phillipson will be education minister.
Live from Downing Street: Watch my first speech as Prime Minister — Keir Starmer (@Keir_Starmer) https://t.co/t2fQjytLBHJuly 5, 2024
Labour won a massive majority in the 650-seat parliament, prompting Rishi Sunak's resignation on Friday morning, before Starmer went to meet King Charles and be formally named prime minister.
He said he would fight every day to rebuild trust, saying the UK would have a "government unburdened by doctrine," underlining something he had repeated during the campaign - that he would put country first, party second.
"To defy, quietly, those who have written our country off. You have given us a clear mandate, and we will use it to deliver change."
The election result has up-ended UK politics.
Labour won more than 410 seats, an increase of 211, while the Conservatives lost 250 MPs, including a record number of senior ministers and former prime minister Liz Truss.
