NCSA may refer to:

• National Cadet Special Activities, aviation programs run by the American Civil Air Patrol
• National Center for Supercomputing Applications, a computer science research center in Urbana, IL
  • NCSA Common log format, a file format for log files produced by web server software
  • NCSA HTTPd, a web server that introduced the Common Gateway Interface
  • NCSA Mosaic, an early web browser instrumental to the popularization of the World Wide Web
  • NCSA Telnet, a software implementation of the Telnet protocol
  • University of Illinois/NCSA Open Source License, a free software license
• National Center for Supercomputing Applications (Bulgaria), a computer science research center in Sofia, Bulgaria
• National Child Search Assistance Act, a United States federal law enacted in 1990
• National Cyber Security Authority (Israel), a government organization merged into the Israeli National Cyber Directorate
• NATO Communications and Information Systems Services Agency, a deactivated agency, formerly within NATO
• Next College Student Athlete, a company facilitating collegiate athletic recruiting
• North Central Sociological Association, a regional American professional organization