  While the tip of the red giant branch (TRGB) has been used as a distance
indicator since the early 1990's, its application to measure the Hubble
Constant as a primary distance indicator occurred only recently. The TRGB is
also currently at an interesting crossroads as results from the James Webb
Space Telescope (JWST) are beginning to emerge. In this chapter, we provide a
review of the TRGB as it is used to measure the Hubble constant. First, we
provide an essential review of the physical and observational basis of the TRGB
as well as providing a summary for its use for measuring the Hubble Constant.
More attention is then given is then given to recent, but still pre-JWST,
developments, including new calibrations and developments with algorithms. We
also address challenges that arise while measuring a TRGB-based Hubble
Constant. We close by looking forward to the exciting prospects from telescopes
such as JWST and Gaia.
