In this paper, the use of carbon fiber composite (CFC) materials is investigated for building antennas and microwave circuits, by replacing the metal with CFC. Two kinds of composite materials are investigated, namely reinforced continuous carbon-fiber (RCCF) composites and carbon nanotube (CNT) composites. We use RCCF composite to build ultra-wideband antennas. The effect of the anisotropic conductivity tensor of RCCF composite on the antenna performance is investigated. As one of the most highly-conductive composites, single wall carbon nanotube (SWCNT) buckypapers are used to build composite antennas. A new fabrication method is proposed to print arbitrarily-shaped full-composite SWCNT antenna on any type of substrate. Various types of SWCNT antennas are fabricated for different wireless antenna applications. Good agreement is demonstrated between simulated and measured performance for all these composite antennas.