The former federal prosecutor was nominated to fill the post left vacant one month ago by Comey, who is set to be grilled by lawmakers Thursday over allegations the president sought to interfere with the FBI's Russia probe before sacking him.
"I will be nominating Christopher A. Wray, a man of impeccable credentials, to be the new Director of the FBI. Details to follow," Trump tweeted.
Wray served as assistant attorney general in charge of the Justice Department's criminal division under president George W. Bush, from 2003 to 2005, working closely with the FBI.
He will have limited power to influence the agency's Russia investigation, which was placed in the hands of an independent prosecutor -- former FBI director Robert Mueller -- following Comey's dismissal.
Trump's announcement was timed a day ahead of Comey's highly-anticipated testimony to the Senate Intelligence Committee on the investigation into Russian interference in the 2016 US elections and possible collusion with Trump's campaign.
Comey is expected to dispute Trump's claim that the then-FBI chief told him multiple times that he was not under investigation, CNN reported, citing sources familiar with Comey's thinking.
But Comey will also be pressed over reports, citing private notes he wrote, that in three meetings and phone calls in January and February, Trump urged him to halt or ease up on the Russia probe's focus on his former national security advisor Michael Flynn.
In addition, media reports say he pressured several top officials, including Director of National Intelligence Dan Coats, to intervene in the investigation on Flynn's behalf.
Coats is one of three officials coming under the spotlight in hearings taking place Wednesday, along with National Security Agency head Mike Rogers and interim FBI Director Andrew McCabe.
In a statement late Tuesday, a spokesman for Coats said he "has never felt pressured by the president or anyone else in the administration to influence any intelligence matters or ongoing investigations."
Fears of politicization
No definitive evidence of collusion between Trump's campaign and Russia has yet come to light, and there have not been any formal accusations that Trump sought to obstruct the investigation.
But the allegations have drawn comparison to the 1970s Watergate scandal, in which president Richard Nixon, facing possible impeachment over obstruction of justice charges, was forced to resign.
If his nomination is approved by the Senate, Wray will take hold of an agency generally dismayed at Trump's treatment of Comey and concerned about the possible politicization of the Russia investigation.
The FBI Agents Association had urged Trump to nominate someone who has worked in their ranks.
Wray will also be partnered with Attorney General Jeff Sessions in carrying out Trump's call for a crackdown on violent crime and immigration, and taking a hard line against people who leak classified information.
On Monday the Justice Department announced the arrest of 25-year-old intelligence contractor Reality Winner on charges she violated the espionage act by leaking a top secret report from the National Security Agency on Russian election meddling.
Represented Trump ally
Since leaving the Justice Department, Wray has worked on mostly white collar civil and criminal cases as a partner at King & Spalding law firm in Washington and Atlanta.
He most notably represented New Jersey Governor and Trump ally Chris Christie in the 2013 scandal over the closure of a key bridge to hurt Christie's political rivals.
At King & Spalding, the Yale Law School graduate chairs a unit representing entities and individuals in white collar criminal and regulatory enforcement issues, civil litigation and internal corporate investigations, according to the law firm's website.
At the Justice Department, he helped handle corporate fraud scandals, served on Bush's Corporate Fraud Task Force and oversaw major fraud investigations including that of energy giant Enron.
He also helped coordinate the agency's response to the September 11, 2001 attacks.
