GPS Block IIIA, or GPS III is the next generation of GPS satellites, which will be used to keep the Navstar Global Positioning System operational. Lockheed Martin is the contractor for the design, development and production of the GPS III Non-Flight Satellite Testbed (GNST) and the first eight GPS III satellites. The United States Air Force plans to purchase up to 32 GPS III satellites. GPS IIIA-1, the first satellite in the series, was projected to launch in 2014, but significant delays have pushed the initial launch to the spring of 2018.

The United States' Global Positioning System (GPS) reached Fully Operational Capability on July 17, 1995, completing its original design goals. However, additional advances in technology and new demands on the existing system led to the effort to modernize the GPS system. Announcements from the Vice President and the White House in 1998 initiated these changes. In 2000, the U.S. Congress authorized the effort, referred to as GPS III.

The project involves new ground stations and new satellites, with additional navigation signals for both civilian and military users, and aims to improve the accuracy and availability for all users.

Lockheed Martin was awarded the GPS III Space Segment contract on May 15, 2008. The first launch was projected for 2014, due to multiple delays, the date has slipped to spring 2018.Raytheon was awarded the Next Generation GPS Operational Control System (OCX) contract on Feb 25, 2010.

Block IIIA satellites use Lockheed Martin's A2100 bus structure. The propellant and pressurant tanks are manufactured by Orbital ATK from lightweight, high-strength composite materials. Each satellite will carry 8 deployable JIB antennas designed and manufactured by Northrop Grumman Astro Aerospace

The first GPS III satellite was originally scheduled for launch in 2014, but in December 2016 the Director of the U.S. Air Force's Global Positioning Systems Directorate announced the first satellite will launch in the spring of 2018. The delays have been caused by a number of factors, primarily due to issues found in the navigation payload.

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