It's hard to say, but the most likely candidate would be 1973 Triple Crown winner Secretariat. The big chestnut colt set records in the Kentucky Derby and Belmont that may never be broken.
Secretariat was the fastest horse that ever lived
1:59.4 was he fastest and was a record set by Secretariat "The Greatest Horse That Ever Lived" at the Kentucky Derby.
The fastest person who ever lived is Usain bolt.
The cast of The Fastest Man Who Has Ever Lived - 2010 includes: Usain Bolt as himself
Alvin Lee
I think Phar Lap
UB is the fastest person ever timed for a 100m or 200m track race. is he the fastest human ever alive? We will never know.
Man o' War
Twister type him in on youtube/google
Fritz the Horse went by The Greatest All-Round Horse That Ever Lived.
SECRETARIAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! the best horse ever he holds all records at the Kentucky derby and at the preekness and by 2 second at the belmont he is the best horse ever
The oldest horse that ever lived was a Thoroughbred named Old Billy. He lived until he was 62 and he died in 1823.