XSI may refer to: Softimage XSI, a high-end three-dimensional (3D) graphics application South Indian Lake Airport, the IATA code for the airport in Canada Canon EOS 450D, known as EOS Rebel XSi in North America, a DSLR camera from Canon X/Open System Interfaces Extension, a supplementary specification to the Single UNIX Specification A conventional XML namespace prefix for XML Schema instance information Broadsoft Xtended Services Interface, a set of APIs for integrating BroadWorks functions with Internet services