The HST Treasury Program on the Orion Nebula Cluster has been recently completed (May 2005). Using 104 orbits of HST time we have imaged a field ${\sim }1/6$ of a square degree nearly centered on the Trapezium stars. The survey, made with ACS, WFPC2 and NICMOS-Camera 3 in parallel, has imaged this cornerstone region with unprecedented sensitivity (23-24 mag), dynamic range (${\sim}12$ mag), spatial resolution (50mas), and wide spectral coverage (9 filters from U to H). We have assembled the richest, most accurate and unbiased dataset of stellar photometry for pre-main-sequence objects ever obtained, an essential tool for understanding of the star formation process in regions dominated by massive OB stars.
