The terahertz (THz) region of the electromagnetic spectrum is of great importance for astrophysics. In fact, it is central to the whole field of experimental cosmology. This paper outlines the range of astrophysical problems that can be answered by observing at THz frequencies, describes some of the major THz astronomical telescopes that are being constructed, and gives a vision of the way in which the technological development of superconducting very-large-scale integration circuit technology and solid-state source technology will lead to major advances in the subject.