Manchester United's American owners say they will "explore strategic alternatives" for the club "including new investment into the club, a sale, or other transactions".
The Glazer family bought the Old Trafford outfit for £790m ($1.34bn) in 2005.
"The process is designed to enhance the club's future growth, with the ultimate goal of positioning the club to capitalise on opportunities both on the pitch and commercially," a United statement said.
In 2012, the Glazers sold 10% of their holding via a stock listing and have sold further shares in the following years.
More to follow.
