ARJ (Archived by Robert Jung) is a software tool designed by Robert K. Jung for creating high-efficiency compressed file archives. ARJ is currently on version 2.86 for DOS and 3.20 for Windows and supports 16-bit, 32-bit and 64-bit Intel architectures.
ARJ was one of two mainstream archivers for DOS and Windows during the early and mid-1990s, with PKZIP being its competition. Parts of ARJ were covered by . Generally ARJ was less popular than PKZIP, but it did enjoy a niche market during the BBS era and in the warez scene. This was largely due to ARJ's creation and handling of multi-volume archives (archives which are split into smaller files which are then suitable for dial-up transfers and floppy distribution) being more robust than PKZIP's.
ARJ may refer to:
- ARJ, a compressed file format
- ARJ, the IATA code for Arso Airport, Indonesia
- The Comac ARJ21 Advanced Regional Jet