The 31-year-old is set to sign a two and a half year deal with the club, per Sky Sports.
Ighalo is set to transfer from Shanghai Shenhua, where he returned after his loan spell ended in January at United.
The Nigerian managed five goals in 23 games for the Red Devils, and fulfilled his lifelong ambition of playing for the club he supported his whole life.
Now he will be hoping to secure what could be the last major contract of his career with Al-Shabab.
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