The 2004 World Thoroughbred Racehorse Rankings was the inaugural edition of the World Thoroughbred Racehorse Rankings. It is an assessment of racehorses which was issued by the International Federation of Horseracing Authorities (IFHA) in January 2005. It includes horses aged three or older which raced or were trained during 2004 in countries where the flat racing year runs from January 1 to December 31. These countries are generally in the Northern Hemisphere.
The ratings represent a weight value in pounds, with higher values given to horses which showed greater ability. It is judged that these weights would equalize the abilities of the horses if carried in a theoretical handicap race. The list includes all horses rated 115 or above, and it also shows the surface and the distances at which the rating was achieved.
The highest rating in the 2004 season was 130, which was given to the performance of Ghostzapper in the Breeders' Cup Classic. In total, 162 horses were included in the list.