Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity.  While most experimental searches focus on Weakly Interacting Massive Particles (WIMPs) with masses above the proton (about 1 GeV/c^2), many natural dark-matter candidates have masses below the proton and are invisible in traditional WIMP searches.  In this talk, I will discuss the search for dark matter with masses between about 500 keV/c^2 to 1 GeV/c^2 (“sub-GeV dark matter”), which has seen tremendous progress in the last few years.  I will describe several direct-detection strategies, including searching for dark matter interactions with electrons in noble liquids, semiconductors, and scintillators.  I will in particular highlight SENSEI, a funded experiment that will use new ultra-low-threshold silicon CCD detectors (“Skipper CCDs”) capable of detecting even single electrons.  I will describe the first results from SENSEI, and how we expect to probe orders of magnitude of novel dark matter parameter space in the next few years.