Phimachus was a shepherd in the service of king Actor. He sheltered Philoctetes on the island of Lemnos and for ten years dressed his wound that he had received as the result of being bitten by a snake. Phimachus thus has a name that means 'pain muzzier', from phimos, 'muzzle' (as for a dog), 'nose-bag' (for a horse) and achos, 'pain', 'ache'.

No doubt it was necessary to 'muzzle' the wound since the bite had festered and so gave off an unpleasant stench. (It was as a result of this that Agamemnon had ordered Philoctetes to be 'isolated' on Lemnos.) Philoctetes' wound was finally cured by either Machaon or Podalirius.