The OPTICON Alliance is an alliance of small-to-medium-aperture telescopes led from IA-FORTH in Heraklion, with historical roots in OPTICON, the Optical Infrared Coordination Network for Astronomy, which was coordinated from Cambridge, UK from 2000 with EC funding support. 

One of the early activities established the first forum for the Directors of all of Europe's optical-infrared telescopes which provided open-access TransNational Access to their facilities. This Telescope Directors' Forum - TDF - flourished and proved highly valued. 

From 2010 a network of smaller telescopes developed within OPTICON, which were able to contribute to Time Domain Astronomy, facilitated by central data processing and archiving, simple no-proposal user access, and central target provision, initially for science support to transient discoveries. This activity has grown into the 100+ telescopes which contribute through the BHTOM activity. 

The combination of the facilities in the TDF and those in BHTOM together form the OPTICON Alliance. Membership is being expanded more widely.