Ithomi is a municipal unit (dimotiki enotita) of the municipality (dimos) of Messini within the regional unit (perifereiaki enotita) of Messenia in the region (perifereia) of Peloponnese, one of 13 regions into which Greece has been divided. Before 2011 the same hierarchy prevailed, according to Law 2539 of 1997, the Kapodistrias Plan, except that Messenia was a nomos and Ithomi a demos, with seat in Valyra. The lowest-level units were the same with the same populations in either system but where before 2010 they were Local Divisions, after it they were Local Communities.