An atlas of supernova remnant candidates in Messier 31.

Narrow band CCD imagery in Hα and [SII] of a large fraction of the spiral arms in the Northeast half of Messier 31 has been used to isolate a sample of 52 "forbidden-line" supernova remnant (SNR) candidates for which the integrated ratio [SII]: Hα > 0.5. An atlas of images in these emission lines, red optical continuum and 1465 MHz radio continuum is presented, together with the tabulated integral properties of these sources. Assessing the completeness of the sample yields a crude estimate of the massive supernova rate (due to stars more massive than 7 M_sun_) of 1 in 80 yr. The range of measured luminosities in both Hα and radio continuum is fully consistent with those found for "forbidden-line" SNR in Messier 33, the LMC and the Galaxy. With the inclusion of our candidates the number of extragalactic SNR (with well- known distances) now exceeds the number of known galactic SNR.