CIDR stands for Classless Inter-Domain Routing, a method for allocating IP addresses and routing Internet Protocol packets.
CIDR may also refer to:
Biology and medicine Controlled internal drug release, devices used in livestock for the synchronization of estrus Center for Infectious Disease Research at the University of Wisconsin Center for Global Infectious Disease Research, now a part of the Seattle Children's Research Institute Not to be confused with the Center for Infectious Disease Research and Policy at UMinn
Miscellaneous other uses CIDR-FM, an FM radio station in Windsor, Ontario, Canada