Messenia (;
Messinia, ) is a
regional unit (
perifereiaki enotita) in the southwestern part of the
Peloponnese, one of 13 regions into which
Greece has been divided by the
Kallikratis plan, implemented 1 January 2011. Before 2011 Messenia was a
nomos (
prefecture). The capital and the biggest city of Messenia in either case has been the city of
Kalamata.