RBU may refer to:
- RBU-6000 Smerch-2, a 213 mm caliber Soviet anti-submarine rocket launcher
- Dell Remote BIOS Update
- Rock Band Unplugged, a rhythm game for PlayStation Portable
- RBU (radio station), a longwave time signal transmitted from Moscow on 66.66 kHz.
RBU is a time code radio station located in Moscow . It transmits a continuous 10 kW time code on 66⅔ kHz. This is commonly written as 66.66 or 66.666 kHz, but is actually 200/3 = 66.6̅ kHz. Until 2008, the transmitter site was near Kupavna and used as antenna three T-antennas spun between three 150 metres tall grounded masts. In 2008, it has been transferred to the Taldom transmitter at .