HAT-P-26 is a K-type main-sequence star about 466 light-years (143 parsecs) away. A survey in 2015 did not find any stellar companions in orbit around it,^[5] although a red dwarf companion with a temperature 4000⁺¹⁰⁰
₋₃₅₀ K is suspected on wide orbit.^[6]

The designation HAT-P-26 indicates that this was the 26th star found to have a planet by the HATNet Project.

In August 2022, this planetary system was included among 20 systems to be named by the third NameExoWorlds project.^[7] The approved names, proposed by a team from Puerto Rico, were announced in June 2023. HAT-P-26 is named Guahayona and its planet is named Guataubá, after figures from Taíno mythology.^[8]

In 2010 a transiting hot Neptune like planet was detected.^[4] The transiting planet HAT-P-26b was detected by the HATNet Project using telescopes located in Hawaii and Arizona. The planet is likely formed by pebble accretion mechanism.^[9] The transmission spectrum of HAT-P-26b was taken in 2015, with the best fit favouring either a cloudless atmosphere or an atmosphere with a low-lying cloud deck.^[10] The atmospheric composition of the planet was measured in 2019, and a water vapor volume fraction of 1.5^+2.1
_−0.9% was detected. HAT-P-26 is carbon depleted, with a C/O ratio constrained to less than 0.33. Also, the planet's atmosphere contains light metal hydrides.^[11] The measured planetary temperature is equal to 563⁺⁵⁸
₋₅₄ K.

In 2019, a transit timing variation analysis of HAT-P-26b indicated the possible presence of a second planet in the system on a wide, 1141-days orbit.^[12]

In 2023, the atmosphere of the planet was confirmed to contain 12±2% steam at 590⁺²⁰
₋₃₀K.^[13]