High Peak to Average Power Ratio (PAPR) is one of the major drawbacks in Orthogonal Frequency Division Multiplexing (OFDM). The high PAPR increases the complexity of Analogue to Digital (A/D) and Digital to Analogue (D/A) converters and also reduces the efficiency of RF High Power Amplifier (HPA). In this paper, we propose two novel PAPR reduction techniques for OFDM systems, Zadoff-Chu matrix Transform (ZCT) precoding based PAPR reduction technique and ZCT postcoding based PAPR reduction technique. Simulation results show that, at clip rate of 10-1, the PAPR of our both proposed systems reduced to 0dB, 3dB, 4.1dB and 4.3dB for M-QAM (where M = 4, 16, 64, 256). Both ZCT precoding and postcoding based OFDM systems are shown better PAPR gain and Bit Error Rate (BER) performance than Walsh Hadamard Transform precoded OFDM (WHT-OFDM) and OFDM conventional. © 2010 IEEE.