Tenagra Observatory and Tenagra Observatory II are astronomical observatories in Cottage Grove, Oregon and Arizona. The observatories house heavily automated robotic telescopes.

Circa 2016, the observatory was utilized with the Katzman Automatic Imaging Telescope a member of the Lick Observatory and Tenagra Observatory Supernova Searches (LOTOSS).

Beginning in 2018, after a NASA grant to owner Michael Schwartz expired, control of the Arizona observatory was turned over to Gianluca Masi's Virtual Telescope project.

The observatory near Cottage Grove, Oregon was constructed c. 1998, and had a 14-inch (360 mm) Celestron Schmidt-Cassegrain with a SBIG CCD imager, probably upgraded to Apogee Instruments later.

The Arizona observatory at Patagonia, 20 miles from Nogales, began operations in 2000. Tenagra II is a custom-made 32-inch (810 mm) Ritchey-Chretien telescope manufactured by SciTech Astronomical Research, in operation since 2001. "Pearl" is a 16-inch (410 mm) f/3.75 corrected Newtonian. There is also a 24-inch (610 mm) SciTech Ritchey-Chretien, and another 14-inch Celestron.

The Oregon site was in use as of 2004 as a backup site, during the Southwest monsoon season.

The robotic telescopes can image 1,000 galaxies in an evening for supernova discovery. Using the Oregon Tenagra I telescope, its maker became "the first amateur to achieve consistent supernova discoveries" by using a robotic telescope "to patrol hundreds of galaxies each night".

The Oregon observatory reported 77 Minor Planet Electronic Circulars between 1999 and 2002.