Stampede2, generously funded by the National Science Foundation (NSF) through award ACI-1540931, is one of the Texas Advanced Computing Center (TACC), University of Texas at Austin's flagship supercomputers. Stampede2 entered full production in the Fall 2017 as an 18-petaflop national resource that builds on the successes of the original Stampede system it replaces. The first phase of the Stampede2 rollout featured the second generation of processors based on Intel's Many Integrated Core (MIC) architecture. Stampede2's 4,200 Knights Landing (KNL) nodes represent a radical break with the first-generation Knights Corner (KNC) MIC coprocessor. Unlike the legacy KNC, a Stampede2 KNL is not a coprocessor: each 68-core KNL is a stand-alone, self-booting processor that is the sole processor in its node. Phase 2 added to Stampede2 a total of 1,736 Intel Xeon Skylake (SKX) nodes. The final phase of Stampede2 features the replacement of 448 KNL nodes with 224 Ice Lake nodes.