In this study, a high-gain wideband circularly polarized (CP) printed monopole antenna for wireless local-area network (WLAN), worldwide interoperability for microwave access or WiMAX, C-band, and multiple input, multiple output (MIMO) applications was proposed and demonstrated. The proposed antenna structure has an octal-shaped monopole antenna tilted by 20 from its longitudinal axis, excited by coaxial probe feeding, and partial ground plane. To achieve broadband CP performance, the ground plane was redesigned with etching slots. A 1.6-mm-deep FR-4 (Ԑr= 4.3) substrate with dimensions of 70x55 mm2 is used to create and test a prototype of the suggested antenna. The proposed antenna's measurement results satisfy requirements for a broad ARBW of 107%(1.83-6.05 GHz), a broad impedance bandwidth of 139.39%(2-11.2 GHz), and a maximum gain of 7.28 dBi.