This paper presents the design and fabrication of micromachined GaAs membrane supported millimeter-wave passive circuits. A new type of coupled line band-pass filter demonstrator structure for millimeter-wave applications was designed and fabricated on a 2.2 µm thick GaAs membrane. Low insertion losses were demonstrated. Also, GaAs membrane supported Yagi–Uda antenna structures for applications in the millimeter-wave frequency range were designed and manufactured. The technological approach allows the fabrication of three-edge membranes, which support the antenna structures. This topology assures optimum radiation conditions for these endfire-type antennae. The characterization of a 45 GHz and a 60 GHz antenna structure validates the technological approach.