Family name Греган (Gregan 
, Греган 
) , all over the world, is quite a rare cognomen. The last name Греган is characteristic of Ireland, where it is quite a rare surname, Slovakia, and New Zealand. Not in comparison with a country's population, it most frequently occurs in Ireland, the United States, and the United Kingdom. Much less frequently, Греган is the forename as well as the last name.