The Giant Magellan Telescope (GMT) — the product of more than a century of astronomical research and telescope-building by some of the world’s leading research institutions — will open a new window on the universe for the 21st century. Scheduled for completion around 2017, the GMT will have the resolving power of an 80-foot (24.5- meter) primary mirror — far larger than any other telescope ever built. It will answer many of the questions at the forefront of astrophysics today and will pose new and unanticipated riddles for future generations of astronomers.