In a post on Tuesday, the US mission in Nigeria said Mills’ last day was Friday. He was confirmed as US ambassador to Nigeria in May 2024.
Envoys typically remain at their posts for between three and four years.
However, a diplomatic shake-up in December saw several US ambassadors withdrawn from their posts.
Over two dozen countries were said to be affected, with Africa the most impacted continent.
Mills’ recall came amid frosty US–Nigeria relations over visa disputes and security concerns.
The recall also occurred as both sides were making efforts to partner on initiatives to strengthen bilateral relations.
State Department officials said the recalled ambassadors would not lose their foreign service jobs but would return to Washington for other assignments should they wish to take them.
