Lockheed Have Blue was the code name for Lockheed's proof of concept demonstrator for a stealth bomber. Have Blue was designed by Lockheed's Skunk Works division, and tested at Groom Lake, Nevada. The Have Blue was the first fixed-wing aircraft whose external shape was defined by radar engineering rather than by aerospace engineering. The aircraft's faceted shape was designed to deflect electromagnetic waves in directions other than that of the originating radar emitter, greatly reducing its radar cross-section.

To design the aircraft, the Skunk Works' design team leveraged the mathematics published by Soviet physicist and mathematician Petr Ufimtsev regarding the reflection of electromagnetic waves. A stealth engineer at Lockheed, Denys Overholser, had read the publication and realized that Ufimtsev had created the mathematical theory and tools to do finite analysis of radar reflection.

The eventual design characteristically featured faceted surfaces to deflect radar waves away from a radar receiver. It had highly-swept wings and inward-canted vertical stabilizers, which led to it being nicknamed "the Hopeless Diamond"—a pun on the Hope Diamond. The first operational aircraft made its maiden flight on 1 December 1977.

Two flyable vehicles were constructed. Both were lost due to mechanical problems. Nevertheless, Have Blue was deemed a success, paving the way for the first operational stealth aircraft, Senior Trend, or Lockheed F-117A Nighthawk.