According to Wiki, there are these specific named gods:

Indian: https://en.wikipedia.org/wiki/Hayagriva

Chinese: https://en.wikipedia.org/wiki/Ox-Head_and_Horse-Face

The closest I saw was supposedly a half-horse/half-human 'kinnara' from Indian mythology, but it had no sources and none of the art in the main article depicts anything like this. I am disinclined to believe it to be factual.

I am not certain if a creature beyond a specific god was ever made in any mythology. As such, if you need the word in a creative project, having your created word following the etymology of any other mythical creatures that feature in the project could be one way to go about naming it.

How about horseman? There's an animated series on Netflix called Bojack Horseman, and the main character is indeed a man with a horse's head. The word also has the benefit of being easy to understand without use of Classical Mythology, or classical languages.

Apparently, Tikbalang. In Filipino folklore. Western mythos doesn't seem to have one.... but the Philippines does.

That's called Ipotane.

Ipotane — Google

---

Ipotane:

In Greek mythology, an ipotane was a member of a race of half-horse, half-humans. The ipotanes are considered the original version of the centaur.

— Wikipedia

---

Or reverse-centaur (1, 2) as suggested by Greybeard

---

Hayagriva: Hayagriva, also spelt Hayagreeva (IAST: hayagrīva, literally 'Horse-neck'), is a horse-headed avatar of the Lord Vishnu in Hinduism.

Hayagriva — Wikipedia

Tikbalang, a native folklore in our place here in Philippines which I always thought Minotaur. Apparently, I figured these two were different.