HMDS may refer to:
either of two related reagents in organometallic chemistry: Hexamethyldisilazane ([(CH3)3Si]2NH) Hexamethyldisilazide ([(CH3)3Si]2NM) M = Li as in Lithium bis(trimethylsilyl)amide (LiHMDS) M = Na as in Sodium bis(trimethylsilyl)amide (NaHMDS) M = K as in Potassium bis(trimethylsilyl)amide (KHMDS) Hexamethyldisiloxane (O[Si(CH3)3]2) Her Majesty's Diplomatic Service, of the United Kingdom Helmet mounted display and sight, a system for military pilots Harvest Moon DS, a video game