What is the world's best selling tractor?

Depending on the tractor it could be Massey Furguson, Case/IH or Deere.

Overall in total tractor sales, small to large, Massey Ferguson has been #1 selling worldwide since 1962.

The JOHN DEERe model B is the worlds best selling tractor. During its production years it sold a little over 300,000 models.

Actually the Ford 8N is the best selling tractor with 500,000 made during its production years. The Farmall H is #2 with 391,227 produced.