Tagmatarkhis (Ταγματάρχης, abbreviated as Τχης) is used in the Greek language to mean "Major". Officers holding this rank are typically addressed as "Kyrie Ypodiikita" (Κύριε υποδιοικητά) (stressed on the last syllable), by their subordinates when serve as battalion executive officers, or as "Kyrie Tagmatarcha" ("Κύριε Ταγματάρχα") (stressed on the syllable before last) in other cases.

The name was used in ancient times to signify the commanding officer of a tagma (battalion), alghough nowadays battalions are typically commanded by Lieutenant Colonels. The rank was roughly equivalent to the Legatus of a Roman legion.

In the modern Hellenic Army the rank is superior to an Lokhagos (Captain) and inferior to an Antisyntagmatarkhis (Lieutenant Colonel). The insignia consists of a flaming grenade and a golden star. The average modern tagma consists of three main companies with uniform equipment, a heavy weapons company and a command company which is responsible for the [logistics] of the tagma.