Richardson said he had been unable to establish a strong working relationship with the executive team and that it was in the best interests of the retailer for him to step down now that the company had appointed a complement of advisors.
Non-executive director Simon Bentley has been appointed acting chairman until a permanent replacement is found. The company said it remained committed to strengthening its board further and that it was seeking another non-executive director.
Separately, Sports Direct has appointed Financial Dynamics and its financial communications advisors. The retailer said it was committed to improving the company's external relations with all its stakeholders and its overall corporate governance.
Sports Direct International chief executive Dave Forsey said: 'We would like to thank David for his role in the listing of Sports Direct and wish him all the best in the future. In addition we would like to welcome our new set of advisers and, with their help, look forward to strengthened relations with the City and our shareholders.'