The European Southern Observatory (ESO) has signed contracts with Schott and Safran Electronics & Defense to manufacture mirrors for its Extremely Large Telescope (ELT). The optical system of ESO's Extremely Large Telescope consists of five mirrors, each of which represents its own significant engineering challenge. The 39-m primary mirror, which will be made up of 798 individual hexagonal segments each measuring 1.4 m across, will be the largest ever made for an optical telescope. Together, the segments will collect tens of millions of times as much light as the human eye. The contracts to manufacture and polish the telescope’s primary mirror segments were signed by ESO's Director General Tim de Zeeuw and senior representatives of Schott and Safran Reosc, a subsidiary of Safran Electronics & Defense, in the presence of key ESO staff members. The first contract was signed with Christoph Fark, executive vice president of advanced optics at Schott, and Thomas Westerhoff, director of strategic marketing for Schott’s Zerodur. The second contract was signed by Philippe Rioufreyt, CEO of Safran Reosc. The 798 hexagonal segments that together comprise the ELT's primary mirror will be produced from the low-expansion ceramic material Zerodur. Previously, Schott was also awarded the contracts for the production of the telescope's giant secondary and tertiary mirrors and the material is also being used for the deformable quaternary mirror that is currently under construction. Once the mirror blanks are ready, they will be passed to Safran Reosc for mounting interface design, segment figuring and polishing, integration into support systems and optical testing before delivery. During the polishing process, each segment will be polished until it has no surface irregularity of >10 nm. To meet the challenge of delivering such a large number of polished segments within seven years, Safran Reosc will build up to a peak production rate of one mirror a day. It will set up a dedicated new facility at its Poitiers plant, specializing in the production of high-tech optical and electro-optical equipment. The new contract with Safran Reosc is the second-largest contract for the telescope’s construction and the third-largest contract ESO has ever signed. Safran Reosc will also design, polish and test the telescope’s secondary mirror and tertiary mirror while manufacturing the 2-mm thick deformable shell mirrors that will comprise the telescope’s fourth mirror. ESO is an intergovernmental astronomy organization in Europe and a ground-based astronomical observatory supported Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile.