  We explore the stellar population of M31 in a Spitzer Space Telescope survey
utilizing IRAC and MIPS observations. Red supergiants are the brightest objects
seen in the infrared; they are a prominent evolutionary phase. Due to their
circumstellar envelopes, many of these radiate the bulk of their luminosity at
IRAC wavelengths and do not stand out in the near infrared or optically. Going
fainter, we see large numbers of luminous asymptotic giant branch (AGB) stars,
many of which are known long period variables. Relative to M33, the AGB carbon
star population of M31 appears sparse, but this needs to be spectroscopically
confirmed.
