ITMS may refer to:

• International Thomas Merton Society
• Indian Trails Middle School, a school in Winter Springs, Florida
• Ion trap mobility spectrometry, an instrumental method for chemical detection and analysis
• iTunes Music Store, the former name of the iTunes Store

• 54th Street Theatre
• 54th Street (Washington, D.C.)
• 54th Transport Squadron
• 54th United States Colored Infantry
• 54th Vanier Cup
• 54th (Wessex) Brigade, Royal Field Artillery
• 54th (West Highland) Field Brigade, Royal Artillery
• 54th Yard
• 54 University Avenue
• 54 Ursae Majoris
• 54 Welbeck Street
• 54 (year)
• 54°40' Orphyte
• 54–55 Brompton Square
• 5500 series
• 550 AD
• 5"/50 caliber gun
• 550 CE
• 550 Park Avenue
• 550th Flying Training Squadron
• 550 U.S. 124
• 550 U.S. 192
• 550 U.S. 297
• 550 U.S. 330
• 550 U.S. 372