This paper describes the development, along with detailed phase-noise analysis, of V-band monolithic-microwave integrated-circuit (MMIC) dielectric-resonator oscillators (DROs) achieving state-of-the-art performances. A TE01δ-mode Ba(Mg,Ta)O3 cylindrical dielectric resonator (DR) is directly placed on a MMIC GaAs substrate to avoid the loss and uncertainty of bonding wires. A 0.15-μm AlGaAs-InGaAs heterojunction field-effect transistor with optimized structure is developed as an active device. A design procedure proposed by the authors is employed, which allows us to analyze and optimize circuits in consideration for the output power, phase noise, and temperature stability. A developed DRO co-integrated with a buffer amplifier exhibits a low phase noise of -90 dBc/Hz at 100-kHz offset, a high output power of 10.0 dBm, and an excellent frequency stability of 1.6 ppm/°C at an oscillation frequency of 59.6 GHz, all of which are state-of-the-art performances reported for MMIC DROs above V-band. An experimental and theoretical analysis for the phase-noise-reduction effect of a DR is also addressed.