This paper presents an efficient Fast Walsh-Hadamard-Hartley Transform (FWHT) algorithm that optimally integrates the Walsh-Hadamard Transform (WHT) and Discrete Hartley Transform (DHT) into a single computational framework using a block diagonal structure. The proposed algorithm reduces computational complexity significantly compared to previous concatenative methods by saving real multiplications and additions, making it a valuable tool for various applications, including signal processing and wireless communication systems. The algorithm is detailed with illustrative examples and structured to facilitate understanding of its implementation and benefits.