cossack (1844– after 1862) also known as "the cossack", was a british thoroughbred racehorse and sire. in a career that lasted from july 1846 to june 1849 he ran twenty-two times and won three races. in 1847 he proved himself one of the best british colts of his generation, winning derby and being narrowly beaten in the st leger. although he continued to run well in important staying races for the next five seasons, he failed to win another race and was retired to stud in after running once as an eight-year-old in 1852. no subsequent winner of the epsom derby has run beyond the age of five. he was later exported to stand as a stallion in france.