Microstrip antennas are popular because of their low profile, light weight and low cost but narrow bandwidth and gain are the main disadvantages of this antenna. In this paper Multiband Octagonal Patch Antenna has been designed by ring slot technique for working in nine different frequencies presented in multi band C-band, X-band, Ku-band, K-band, Ka-band, Q-band and U-bands. Main applications of these bands are used in terrestrial microwave communications. In this research work, the performance of octagonal patch antenna operating at 7 different bands is analyzed. The Design methodology of the proposed research carried in 2 major modules. 1. Design of Single Octagonal Ring Slot antenna, 2. Design of Double Octagonal Ring Slot antenna. In the first design a single octagonal ring slot microstrip patch antenna is developed which resonates at six frequencies of five different frequency bands of C-band, Ku-band, K-band, Q-band and U-bands. In the second design a double octagonal ring slot microstrip patch antenna is developed which resonates at nine frequencies of six different frequency bands of X-band, Ku-band, K-band, Ka-band, Q-band and U-bands. The proposed antenna has been simulated by HFSS and measured by combinational analyzer.