ctools is a software package developed for the scientific analysis of Cherenkov Telescope Array (CTA) data, as well as data from existing Imaging Air Cherenkov Telescopes (such as H.E.S.S., MAGIC or VERITAS). ctools comprises a set of ftools-like binary executables and Python scripts with a command-line interface allowing for interactive step-wise data analysis. ctools includes also Python modules to control all tools and scripts from within Python. Creation of shell or Python scripts and pipelines is supported as well. ctools are based on GammaLib, a versatile toolbox for the scientific analysis of astronomical gamma-ray data. Besides CTA, GammaLib supports the analysis of H.E.S.S., MAGIC, VERITAS, Fermi/LAT, COMPTEL and INTEGRAL/SPI data. GammaLib supports in particular the combination of data from different instruments in a true joint multi-wavelength analysis that consistently handles the response of each instrument. An interface to virtual observatory ressources does also exist.