Republican presidential contender Donald Trump has picked Indiana governor Mike Pence as his running mate.
Mr Trump revealed his decision on Twitter and said he will hold a news conference on Saturday morning.
The businessman had originally planned to announce his running mate earlier on Friday but he delayed the announcement because of the attacks in Nice.
Mr Pence had already flown to New York before Mr Trump announced the postponement.
The staunchly conservative 57-year-old served six terms in Congress before being elected governor and could help Mr Trump navigate Capitol Hill.
He is well-regarded by evangelical Christians, particularly after signing a law that critics said would allow businesses to deny service to gay people for religious reasons.
Mr Trump's announcement came about an hour before a deadline for Mr Pence to withdraw from his re-election race in Indiana. State law prohibits candidates from being on the ballot in two races.
His hectic decision-making process was made more complicated by the fact that the businessman was in California on Thursday for a series of fundraisers, isolated from nearly all of his closest advisers, including his three adult children and his campaign chairman, Paul Manafort.
Frustration for Mr Trump and his advisers mounted because of news reports that Mr Pence was the pick, sending top aides scrambling to insist no final decision had been made.
The billionaire said in a series of television interviews on Thursday night that he had not yet settled on a "final, final" choice, leaving open the possibility the unpredictable presumptive nominee could change his mind.
But Mr Manafort dismissed suggestions in an interview on Fox News Channel that Mr Trump was having second thoughts about his choice.
Mr Trump's choice of Pence as his running mate adds political experience - and a dose of unflappability - to the Republican presidential ticket.
He will be a reliably conservative number two with a calm demeanour and deep ties to Washington.
Mr Trump also seriously considered offering the running mate post to former House speaker Newt Gingrich and New Jersey governor Chris Christie, according to sources.
Mr Trump was up against the clock in unveiling his pick. In addition to Mr Pence's deadline in Indiana, the Republican convention kicks off in Cleveland on Monday.
Top party officials are already in Cleveland, where a committee voted late on Thursday to rebuff a push to let delegates vote for any presidential candidate they would like. It was a major blow to Republican foes of Mr Trump who have been working to thwart his nomination.
Mr Pence would have the backing of party leaders and ease some of their concerns about Mr Trump's political inexperience and volatile temperament.
Mr Pence also has influential allies in Mr Trump's inner circle but some of his children, who have been closely advising their father, were said to favour different candidates.
Hillary Clinton's presidential campaign said Mr Trump has "doubled down" on what they called his "disturbing beliefs" by choosing Mr Pence as his running mate.
Clinton campaign chairman John Podesta said Mr Pence is "an incredibly divisive and unpopular figure".
He said Mr Pence is known for supporting "discriminatory politics and failed economic policies that favour millionaires and corporations over working families".
Mrs Clinton's campaign said he was an early advocate for the tea party in Congress and, as governor, pushed a law that discriminated against gays and lesbians and alienated businesses in Indiana.
The Clinton team noted Mr Pence led the fight to cut funds from Planned Parenthood and restrict abortion rights and has opposed raising the federal minimum wage.