Abstract. Recent petascale direct numerical simulation (DNS) of turbulent combustion have transformed our ability to interrogate fine-grained turbulence-chemistry interactions in canonical laboratory configurations.  In particular, three-dimensional DNS, at moderate Reynolds numbers and with complex chemistry, is providing unprecedented levels of detail to understand fundamental coupling between turbulence, mixing and reaction.  This information is leading to new physical insight and is providing unique validation data for assessing model assumptions in coarse-grained engineering CFD approaches used to design modern combustors.  The role of petascale DNS is illustrated through selected examples relevant to controlling ignition and combustion rates in homogeneous charge compression ignition engines and to fuel injection processes in stationary gas turbines for power generation.  Petascale simulations presently generate upwards of a petabyte of complex, multi-scale, time-varying data used by combustion modelers to validate subfilter combustion and mixing models in large-eddy simulation.  With the advent of 10-20 petaflop hybrid architectures with accelerators it will be possible to increase the chemical complexity of DNS.  Simulations will move beyond todays studies of simple fuelshydrogen, syngas and methaneto more complex, larger-molecule hydrocarbon fuels like isooctane (a surrogate for gasoline), commercially important oxygenated alcohols (for example, ethanol and butanol), and biofuel surrogates.