The HabEx study has developed a baseline concept for a 4 m aperture next generation space telescope operating from the ultraviolet to the infrared, capable of compelling general astrophysics and exoplanet science. HabEx carries four instruments, a UV spectrometer/imager (UVS) together with a general purpose astrophysics camera/spectrograph (HWC) and for exoplanet work, a coronagraph and a starshade. UVS reaches down to 115 nm with resolution up to 60,000 and a 3'x3' field of view. HWC operates between 370 nm and 1800 nm, again with a 3'x3' field of view; the spectral resolution is 1000 and it carries a suite of science filters. The telescope is capable of tracking both deep space and solar system objects. The coronagraph enables observations and spectroscopy at up to R=140 with instantaneous 20% bandwidth between wavelengths of 450 and 1800 nm and is intended to be used in a survey mode. However, it also backs up most of the functionality of the accompanying starshade instrument which will have superior performance for spectroscopy. The 52 m diameter starshade flies 76,600 km from the telescope and at that range has a broadband suppression of the starlight between 300 and 1000 nm. A single observation at 108% bandwidth covers a very wide spectral band at a resolution up to 140. Both coronagraph and starshade are equipped with integral field spectrometers to enable simultaneous spectroscopy of exoplanets within the field of view. This paper details the design of the telescope, the four science instruments and associated optical systems.