Apsis in an automatic image processing pipeline for the Hubble Space Telescope's Advanced Camera for Surveys (ACS) instrument. The pipeline supports processing of images from the HRC and WFC cameras on the ACS instrument and is written in Python. The processing steps include empirical determination of image offsets and rotation, cosmic ray rejection, image combination using the drizzle routine called via the STScI Pyraf package, object detection and photometry using SExtractor.