The 2009–10 season was 85th season in the existence of Rotherham United F.C., a football club based in Rotherham, South Yorkshire, England.

The club participated in League Two, the FA Cup, the League Cup and the Football League Trophy.

On 9 September 2009, manager Mark Robins left Rotherham to manage local rivals Barnsley.

[1] Later that month, Ronnie Moore was appointed as his replacement.

[2] Players' ages are as of 1 August 2009.