PostprintThis is the accepted version of a paper published in IEEE Microwave and Wireless Components Letters. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record): Abstract-In this letter we report a low phase noise oscillator exhibiting state-of-the-art phase noise characteristics at 60 GHz. The oscillator is stabilized by an off-chip substrate integrated waveguide (SIW) cavity resonator, manufactured in LTCC technology. The area on top of the cavity resonator is used to flipchip mount the MMIC, realized in SiGe technology. Measured oscillators discussed in this paper operate at frequencies of 59.91 GHz, 59.97 GHz and 59.98 GHz. The measured phase noise at 1 MHz offset is −115.76 dBc/Hz, −115.92 dBc/Hz and −116.41 dBc/Hz, respectively. To our knowledge, the present hybrid oscillator has the lowest phase noise and highest figure of merit of integrated oscillators at V-band. The simulations are in very good agreement with the measured oscillation frequencies.