An Optical Multiply Accumulate (MAC) is a fundamental operation in digital signal processing (DSP) and computer arithmetic that involves multiplying two numbers and then accumulating (summing) the results over a series of operations. The "optical" in Optical Multiply Accumulate refers to the use of optical components, such as lasers or optical fibers, to perform this operation, as opposed to electronic components.

Optical Multiply Accumulate can be advantageous in certain applications, particularly those that require high-speed processing or massive parallelism, due to the inherent speed of light and the potential for performing numerous multiplications and accumulations simultaneously using optical components.