In response to an Announcement of Opportunity for new instrumentation for the GTC, an international team led by the University of Florida and composed of scientists and engineers from 8 institutions in 3 countries submitted a proposal for building a highly powerful instrument within the required envelope and budget. The MIRADAS instrument will be a common user NIR multi-object spectrograph equipped with a sophisticated multiplexing system able to deliver spectral resolutions of R~20,000 in the wavelength range 1-2.5 microns for up to 20 objects simultaneously over a field of regard of 5 arcmin diameter. MIRADAS was selected by the GTC Project Office in the autumn of 2010, and work on the Preliminary Design phase began in mid-2011. In this paper, we summarize the main instrumental features and primary science cases for the proposed instrument.