The Brazilian international has departed Aston Villa at least temporarily after making two substitute appearances this season.
Coutinho joined Aston Villa initially on loan from Barcelona in January 2022 before an impressive start led to a permanent transfer for £17m that summer.
The 31-year-old however failed to replicate his early form for the Villains and lost his position in the starting eleven under Unai Emery as a result.
The former Inter Milan and Liverpool playmaker is still contracted to Villa until the summer of 2026.
Coutinho has scored six goals in 43 appearances so far for Aston Villa.
His new club are managed by former Argentina striker Hernan Crespo and are currently third on the Qatari league standings.
Al Duhail won the Qatar Stars League last season.
Coutinho has won 68 caps for Brazil, with his last cap coming in June 2022.
