James Julius Spilker Jr. (August 4, 1933 – September 24, 2019) was an American engineer and a consulting professor in the aeronautics and astronautics department at Stanford University.

During Spilker's leadership at Stanford Telecommunications Inc., he also designed semiconductor (ASICs) Application-specific integrated circuit for error correction, number-controlled oscillators, and quadrature amplitude modulation.

From 2001 until his death in 2019, Spilker was a consulting professor at Stanford University in the electrical engineering and aeronautics and astronautics department.

He was also co-founder and chairman of Rosum, a high-tech company using digital and analog television signals for indoor positioning services and augmentation of GPS.

He was a member of the National Academy of Engineering (NAE) and a Life Fellow of the IEEE for the development of digital satellite communications and navigation systems.

In 2019, James Spilker shared the 2019 Queen Elizabeth Prize for Engineering with three other GPS pioneers (Bradford Parkinson, Hugo Fruehauf, and Richard Schwartz).