The sturdy, stubborn horses are credited with helping to clear the country's rugged woodlands for agricultural land and providing reliable transport for the Finnish Defence Forces in wartime.
However with the decline of their use in farming, the cold-blooded breed's numbers have declined. In recent years there has been an upswing in interest in the breed as an all-around riding horse, suitable for trekking, jumping and even dressage. They are also often used for trotting races.
There are now an estimated 19,500 Finnish horses.
The main celebration on Thursday is at the Equine College of Ypäjä in south-western Finland, which hosts an all-day seminar.
Suomen Hippos, the Finnish Trotting and Breeding Association, urges the flying of the Finnish flag on Thursday to honour the breed.