The Red Devils have welcomed back the Ivorian as they look to finish the season on a high.
United are in the semi finals of the Europa League, where they face off against Roma.
They are also vying for second spot in the Premier League.
Bailly has missed United's five matches since the international break, as he tested positive for COVID-19 with his national side.
"Back to training," stated a caption from Bailly on a post on his Instagram account, per the club website.
"Excited to be back with the team very soon.
"Thanks for all the concern and support messages after being diagnosed with COVID."