Lets start in our own solar bubble and move outward.
The largest moon in our solar system in orbit around Jupiter.
Moving on and we reach “Kepler-1625b-i”, not just a moon, this is an Exomoon with 19.09 times the mass of Earth.
A Neptune-like moon that orbits a massive monster Gas-giant.
This monster moon is in orbit around planet Kepler-1625b, sitting 1AU from its stat and with 11.6 times the mass of Jupiter, making a monster duo.
The star sits just 0.98AU from the gas giant, a spectral clas G and just a little larger than oir own star.
OK, it is a massive struggle to find a moon around a distant planet within an alien star's planetery system, so there will be a larger example someplace, we just need to improve our visual ability's and other things.
We may not have found our targets yet, but there are other candidates.
Kepler-1625b-i
Kepler-1708b-i
WASP-49b-i
809b-I and many MANY more..