Trimarcisia (, ; 'feat of three horsemen') was an ancient Celtic military cavalry tactic or organisation; it is attested in Pausanias's Description of Greece, where he describes the use of trimarcisia by the Gauls during their invasion of Greece in the third century BCE. Available online at the Perseus Project. According to Pausanias: Pausanias's view was that the Gauls had adopted this method of fighting by copying the Persian Athanatoi elite force with the difference that while the Persians waited until after a battle to replace their casualties, the Gauls "kept reinforcing their full number during the height of the action".
Etymology According to Pausanias, was the Celtic name for a horse. This corresponds to the root of words for 'saddle horse' attested in Celtic and Germanic but not in other Indo-European languages, a root that is of uncertain etymology.
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