  This is the first of a series of papers presenting the Modules for
Experiments in Stellar Astrophysics (MESA) Isochrones and Stellar Tracks (MIST)
project, a new comprehensive set of stellar evolutionary tracks and isochrones
computed using MESA, a state-of-the-art open-source 1D stellar evolution
package. In this work, we present models with solar-scaled abundance ratios
covering a wide range of ages ($5 \leq \rm \log(Age)\;[yr] \leq 10.3$), masses
($0.1 \leq M/M_{\odot} \leq 300$), and metallicities ($-2.0 \leq \rm [Z/H] \leq
0.5$). The models are self-consistently and continuously evolved from the
pre-main sequence to the end of hydrogen burning, the white dwarf cooling
sequence, or the end of carbon burning, depending on the initial mass. We also
provide a grid of models evolved from the pre-main sequence to the end of core
helium burning for $-4.0 \leq \rm [Z/H] < -2.0$. We showcase extensive
comparisons with observational constraints as well as with some of the most
widely used existing models in the literature. The evolutionary tracks and
isochrones can be downloaded from the project website at
http://waps.cfa.harvard.edu/MIST/.
