A true random number generator (tRNG) is proposed that, for the first time, uses the random physical process of time to oxide breakdown under voltage stress. Time to breakdown is repeatedly measured with a counter and serialized into a bitstream. The 1200 μm$^textrm2$ tRNG, called OxiGen, was fabricated in 65 nm CMOS, passes all 15 NIST randomness tests without post-processing and in a 3 month run generated sufficient bits for worst-case expected internet use while being textless;10% exhausted.