Manchester United's owners the Glazer family say they are considering selling the club as they "explore strategic alternatives".
It comes after years of protest from fans against their ownership.
A statement from the club said the board will "consider all strategic alternatives, including new investment into the club, a sale, or other transactions involving the company".
In 2012, the Glazers sold 10% of their holding via a stock listing and have sold further shares in the following years.
"As we seek to continue building on the club's history of success, the board has authorised a thorough evaluation of strategic alternatives," said executive co-chairmen and directors Avram Glazer and Joel Glazer.