This is a printed edition of the official Guile reference manual from the Guile 2.0 distribution. Guile is the official extension language of the GNU Project and is designed to interoperate well with existing programs and libraries written in C. It is an implementation of Scheme, an elegant and conceptually simple dialect of Lisp. Guile promotes interactive and incremental programming, and supports other language front-ends as well, not just Scheme. Major features of Guile include: R5RS scheme compliance, easy integration with C code, full access to POSIX system calls, unicode support, networking and POSIX threads, dynamic linking and foreign function calls, the Boehm-Demers-Weiser garbage collector, modules and hygienic macros, delimited continuations, tail-call optimisation, bytecode virtual machine and compiler infrastructure. This edition of the Guile manual is published by Network Theory Ltd.