The National Defense Service Medal (NDSM) is a service award of the United States Armed Forces established by President Dwight D. Eisenhower in 1953. It is awarded to every member of the U.S. Armed Forces who has served during any one of four specified periods of armed conflict or national emergency from June 27, 1950 through December 31, 2022. Combat or "in theater" service is not a requirement for the award.

The ribbon for the NDSM is 1 3/8 inches wide and consists of the following stripes:

• 1/8 inch wide yellow stripe
• 1/8 inch wide white stripe
• 1/8 inch wide blue stripe
• 1/8 inch wide white stripe
• 1/4 inch wide red stripe
• 1/8 inch wide white stripe
• 1/8 inch wide blue stripe
• 1/8 inch wide white stripe
• 1/8 inch wide yellow stripe

The NDSM is worn centered on the left breast of the uniform, below any campaign medals. A bronze service star is worn on the ribbon for each additional qualifying period of service.

The NDSM is a relatively common award, having been awarded to over four million service members since its inception. It is a symbol of service and sacrifice, and is a reminder of the sacrifices made by all those who have served in the United States Armed Forces.