ACIS may refer to:

• ACIS (Alan, Charles, Ian's System), a solid modelling geometric modeling kernel that several CAD packages use
• Advanced CCD Imaging Spectrometer, an instrument on NASA's Chandra X-ray Observatory
• Algoma Central Railway, which has the reporting mark "ACIS"
• Acoustic Control Induction System, a Variable Length Intake Manifold|variable induction system developed by Toyota
• Applied Climate Information System, a software system developed by NOAA's Regional Climate Centers (RCC)
• Acis, a character in Greek mythology
• Acis (plant), a genus of flowering plants
• ACIS (Adenocarcinoma in situ) on pap smear = grade 3 cervical intraepithelial neoplasia
• ACIS is a professional designation for associates of the Institute of Chartered Secretaries and Administrators

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