Flake's appointment comes as Washington tries to mend ties with its Nato ally.
Jeff Flake, a former senator and one of the most outspoken Republican foes of Donald Trump, was nominated by President Joe Biden as ambassador to Turkey, tasked with managing tense relations with an ally.
Biden met Turkey's President Recep Tayyip Erdogan last month as the two Nato allies tried to iron out differences on a host of issues ranging from Ankara's purchase of Russian missiles to Washington's backing of YPG terrorists in Syria.
Flake, who unlike many Republicans has never retracted his criticism of Trump and went so far as to campaign for Biden in last year's election, said on Tuesday he was "humbled and honoured" to be chosen as ambassador.
"With this nomination, the Biden administration reaffirms the best tradition of American foreign policy and diplomacy: the credo that partisan politics should stop at the water's edge," Flake wrote in a blog post.
His nomination was announced in a routine White House statement as Biden fills out key diplomatic posts, many of them vacant six months into his term.
Turkey has experienced major tensions with Washington in recent years but is also a vital partner in key areas such as Afghanistan.