Over the past 15 years, astrophotonics—the interface between photonics and astronomical/space instrumentation—has led to important advances in adaptive optics, laser communications, interferometry, vortex coronography, precision spectroscopy through fibre etalons, filtering through photonic lanterns and multi-core fibre gratings, and so on. There is an important role here for nanophotonics if nano-patterning can be achieved over large surfaces (~100 mm OD). These advances will be exploited by a new generation of astronomical instruments, as we describe. The case for photonics becomes even more compelling in an era of extremely large telescopes (25-42 m aperture) now under construction.