A 10 MW gyroklystron is being developed for W‐Band accelerator research by Calabazas Creek Research, Inc. through a grant from the U.S. Department of Energy. The device will operate at 91.386 GHz and be tested at Stanford Linear Accelerator Center. The gyroklystron will operate at 500 kV and produce 1.5 microsecond pulses at a 120 Hz repetition rate. Predicted gain and efficiency are 56 dB and 36%, respectively. The circuit consists of six cavities, two operating in the fundamental TE01 mode and the remaining four at the second harmonic TE02 mode. The output is converted to a combination of modes that allow propagation across a 1 cm gap between the body and collector, allowing depressed collector operation. The mode combination also allows implementation of a right angle mirror to redirect the output power into a vertical window and protect the window ceramic from electron impact. The gyroklystron is currently being constructed for initial testing. Progress to date is reported.