Keogh, along with Derby players Mason Bennett and Tom Lawrence, were involved in a car crash that the club described as "an alcohol-related incident" on 25 September.
Bennett and Lawrence were subsequently charged with drink-driving, while Keogh sustained a season-ending knee injury.
The club has now sacked Keogh follwing an internal investigation.
In a statement, they said: "Derby County Football Club has completed the disciplinary hearing regarding Richard Keogh in respect of his involvement in the events of Tuesday, September 24.
"As a result of that process, Mr Keogh has had his contract terminated with immediate effect for gross misconduct. He has the right of appeal within 14 days.
"As we have said from the outset, the club will not tolerate any of its players or staff behaving in a manner which puts themselves, their colleagues, and members of the general public at risk of injury or worse, or which brings the club into disrepute.
"The club will be making no further comment at this time regards this matter, until the conclusion of any potential appeal."
Keogh joined Derby from Coventry City in July 2012 and his contract was due to expire at the end of the 2020-2021 season.