A joint European-Japanese project is proposed to implement SPICA, an infrared space observatory with a large, cryogenically cooled telescope designed to achieve for the first time truly background limited performance, for launch and operations at the end of the next decade. With a 2.5-meter primary mirror actively cooled to below 8K, combined with a new generation of ultra-sensitive detectors, SPICA will offer the community a unique astronomical facility, able to cover the spectral range from 12 to 230µm to unprecedented depths of a few 10-20 W/m2 for spectroscopy (5σ) in 1 hour. This represents a gain in sensitivity of more than two orders of magnitude over both Spitzer and Herschel, a gigantic leap in capabilities for exploring the Universe. Given its enormous leap in sensitivity and spectroscopic capabilities, SPICA commands an enormous discovery space which will enable scientists to react quickly to new discoveries with ALMA, JWST and ELT’s by exploring a unique spectral range.