Using the Zwicky Transient Facility, in 2021 February we identified the first known outburst of the Black Hole X-ray Transient XTE J1859+226 since its discovery in 1999. The outburst was visible at X-ray, UV, and optical wavelengths for less than 20 days, substantially shorter than its 320-day full outburst in 1999, and the observed peak luminosity was two orders of magnitude lower. Its peak bolometric luminosity was only \(2\times 10^{35}\) erg s\(^{-1}\), implying an Eddington fraction of about \(3\times10^{-4}\). The source remained in the hard spectral state throughout the outburst. From optical spectroscopy measurements we estimate an outer disk radius of 10\(^{11}\) cm. The low observed X-ray luminosity is not sufficient to irradiate the entire disk, but we observe a surprising exponential decline in the X-ray lightcurve. These observations highlight the potential of optical and infrared (O/IR) synoptic surveys to discover low-luminosity activity from X-ray transients.