Mr Trump appointed Matthew Whitaker, formerly Mr Sessions' chief of staff, as acting attorney general under the US Vacancies Reform Act, which lays out general rules for temporarily filling vacant executive branch positions.
Whitaker's views make him a natural fit to replace Sessions, who has attempted to expand religious refusals and rollback LGBTQ legal protections throughout his tenure at the Department of Justice.
The president deflected questions about Sessions' expected departure at a White House news conference Wednesday.
Trump has long expressed frustration with Sessions over his recusal from the Justice Department's Russian Federation investigation.
Mr Sessions, who was an early backer of the Trump campaign, recused himself in March 2017 from overseeing the Russian Federation investigation under a similar rule which prohibits officials from overseeing investigations into subjects with whom they have a "a personal or political relationship".
Sessions had recused himself from overseeing the investigation due to his role on the Trump campaign. Today, he declared victory, taking claim for "Kavanaugh's Revenge" after Democrats failed to win enough seats to have a majority in the Senate.
Trump ducked, saying he'd like to answer that at a later time. The recusal left the investigation in the hands of Rosenstein, who appointed Mueller as special counsel two months later after Trump fired then-FBI Director James Comey. The news added yet another layer to previous reports that the president once speculated about why "my guys" at the "Trump Justice Department" weren't doing more to shield him from Mueller's scrutiny.
Trump actually had sacked Sessions before his mid-day presser at which CBS News's Major Garrett asked him whether Session and Deputy AG Rod Rosenstein had a future in their jobs now that the midterms were over.
Sessions announced his plan to resign in a letter to the White House on Wednesday.
"You can't blame Sessions for recusing himself!"
The swift firing may have also been a way for Mr Trump to get ahead of any efforts from the newly-empowered Democrats to reopen the House intelligence committee's investigation into ties between Mr Trump's campaign team and Russian Federation.
He found satisfaction in being able to reverse Obama-era policies that conservatives say flouted the will of Congress, encouraging prosecutors to pursue the most serious charges they could and promoting more aggressive enforcement of federal marijuana law.
Sessions also touted the Justice Department's efforts to address crime, immigration, and the opioid crisis, among other issues.
Mr Trump had wanted to fire Mr Sessions sooner, reported the Associated Press, but was persuaded by aides not to do so until after the midterm elections as it could have hurt the Republican party at the polls.
Mr Trump had made his unhappiness publicly known, griping that he would not have picked Mr Sessions for the post, had he known the Attorney-General would step aside to allow the "witch hunt" to go on.