  In 2010 May, an intermediate luminosity optical transient was discovered in
the nearby galaxy NGC 300 by a South African amateur astronomer. In the decade
since its discovery, multi-wavelength observations of the misnamed ``SN
2010da'' have continually re-shaped our understanding of this high mass X-ray
binary system. In this review, we present an overview of the multi-wavelength
observations and attempts to understand the 2010 transient event and, later,
the re-classification of this system as NGC~300 ULX-1: a red supergiant +
neutron star ultraluminous X-ray source.
