Abstract-A time-reversal implementation of a transmit waveform preconditioning scheme for optimal clutter rejection in radar imaging is presented. Waveform preconditioning involves determining a map on the space of transmit waveforms, and then applying this map to the waveforms before transmission. Our work applies to antenna arrays with an arbitrary number of transmit-and receive elements, and makes no assumptions about the elements being co-located. Waveform preconditioning for clutter rejection achieves efficient use of power and computational resources by distributing power properly over a frequency band and by eliminating clutter filtering in receive processing. By our time-reversal implementation we avoid the need to obtain an explicit model for the environment in order to compute the preconditioning operator.