This document describes techniques (400, 500, 600) and apparatuses (100, 700) for implementing sensor-based near-field communication (NFC) authentication. These techniques (400, 500, 600) and apparatuses (100, 700) enable a computing device (102) to detect, in a low-power state, environmental variances indicating proximity with an NFC-enabled device (104) with which to authenticate. In some embodiments, various components of a computing device (102) in a sleep state are activated to process environmental variance(s), perform authentication operations, and/or an indicate initiation of authentication operations to a user.