Dijon in France is well known for its method of the making a strong grain mustard called Dijon Mustard (moutarde de Dijon).

So far there's no French town named after a mustard, but the town of Dijon gave its name to the mustard of Dijon which was produced there.

The French city of Dijon is famous for developing a method of making a strong flavoured mustard from mostly Canadian mustard seeds, the process has now been industrialised and Dijon mustard no longer needs to be made in Dijon to carry the name. Moutard de Dijon or Dijon Mustard refers to the method used to make the mustard not where it was made.

in a supermarket, in the condiment section... or on a map

Mustard is made in Dijon