One-time programming (OTP) magneto-resistive random access memory (MRAM) bit cells in a physically unclonable function (PUF) memory in breakdown to a memory state from a previous read operation to provide PUF operations is disclosed. PUF memory is configured to permanently one-time program an initial randomly generated PUF output from PUF MRAM bit cells accessed in an initial PUF read operation, to the same PUF MRAM bit cells accessed in the initial PUF read operation. In this manner, the initial PUF output is randomly generated due to process variations of the PUF MRAM bit cells to maintain an initial unpredictable memory state, but the PUF output will be reproduced for subsequent PUF read operations to the same PUF MRAM bit cells in the PUF memory array for reproducibility. The OTP of the PUF MRAM bit cells can be accomplished by applying breakdown voltage to the PUF MRAM bit cells during programming.