President Trump pardoned on Wednesday his former national security adviser Michael T. Flynn, who had twice pleaded guilty to lying to the F.B.I. about his conversations with a Russian diplomat and whose prosecution Attorney General William P. Barr tried to shut down.

“It is my Great Honor to announce that General Michael T. Flynn has been granted a Full Pardon,” Mr. Trump wrote on Twitter.

The presidential pardon brings to an end the drawn-out legal saga of Mr. Flynn. The Justice Department had moved in the spring to withdraw the charge against him after a public campaign by Mr. Trump and his allies, but the judge overseeing the case, Emmet G. Sullivan, had held up the request to scrutinize its legitimacy.

Though Mr. Trump had said months ago that he was “strongly considering” pardoning Mr. Flynn.