The biggest known black hole in the universe so far is an ultramassive black hole in the galaxy cluster Phoenix A (often just called the Phoenix A black hole), with an estimated mass of around 100 billion times the mass of the Sun.

Quick Scoop

  • Current record-holder (likely): Ultrapmassive black hole in the Phoenix A galaxy cluster, ≈100 billion solar masses (at least ~50% more massive than the famous TON 618).
  • Other giants:
    • TON 618 – about 66 billion solar masses.
* A newly measured “Cosmic Horseshoe” galaxy black hole – about 36 billion solar masses.
  • Size comparison: A black hole of tens of billions of solar masses would have an event horizon larger than our entire solar system.
  • Status: All of these are “biggest known” ; we almost certainly have not found the true biggest black hole in the universe yet.

What is the biggest black hole in the universe?

Astronomers now point to the black hole in the Phoenix A galaxy cluster as the most massive reliably reported candidate, with a mass at least half again larger than TON 618’s ≈66 billion Suns, pushing its mass toward the ~100 billion solar-mass range. This makes it a leading contender for the title of “biggest black hole we’ve found ,” even though the universe may hide even more extreme monsters we cannot yet see.

Before Phoenix A’s black hole rose to prominence, the quasar black hole TON 618 was widely cited as the heavyweight champion, with a mass of roughly 66 billion Suns, inferred from how its quasar disk shines and from spectral measurements. More recent work has also revealed a 36‑billion‑solar‑mass black hole in the Cosmic Horseshoe system, showing that several galaxies harbor “top‑10” ultramassive black holes in a similar size league.

How big is “biggest”? (Quick sense of scale)

  • Stellar‑mass black holes: A few to a few dozen times the Sun’s mass.
  • Supermassive black holes: Millions to billions of Suns (for example, the Milky Way’s Sagittarius A* is about 4 million Suns).
  • Ultramassive black holes (UMBHs): Tens of billions of Suns and beyond, like TON 618 and Phoenix A.

An ultramassive black hole of tens of billions of solar masses would have a shadow (the dark “hole” we’d see in an image) several times larger than our entire solar system, when scaled to the same distance. NASA visualizations show that these giants can dwarf even other supermassive black holes, with some modeled up to and beyond 60 billion solar masses.

Biggest black holes you’ll see in articles and forums

Here are a few famous “contenders” you’ll often see mentioned when people ask “what is the biggest black hole in the universe”:

[3][6] [3] [3] [3] [1] [1] [6] [6] [1] [1]
Black hole / host Approx. mass Type Why it’s famous
Phoenix A (cluster core) ≈100 billion Suns (estimate; > TON 618 by ≥50%) Ultramassive black hole Currently a leading candidate for most massive known black hole.
TON 618 ≈66 billion Suns Quasar black hole Long‑time record‑holder discussed in popular videos and articles.
Cosmic Horseshoe galaxy ≈36 billion Suns Dormant ultramassive black hole One of the top‑10 most massive ever measured; possibly among the very largest.
Other simulated/visualized giants Up to >60 billion Suns in NASA comparisons Supermassive/ultramassive Used in animations to showcase size range of known and candidate monsters.
Sagittarius A* (Milky Way) ≈4 million Suns Supermassive black hole Our own galaxy’s central black hole; tiny compared with ultramassive ones.

How do black holes get this huge?

Astronomers think ultramassive black holes grow through several channels that can all stack together over billions of years:

  1. Steady feeding:
    Gas and dust spiral into the black hole in an accretion disk, converting gravitational energy into light and slowly increasing the mass.
  1. Galaxy mergers:
    When galaxies collide, their central black holes can sink to the center of the new galaxy and merge, building a single, much heavier black hole.
  1. “Rule‑breaking” rapid growth in the early universe:
    Some quasars show black holes that appear to be gobbling matter much faster than standard theory (the “Eddington limit”) says they should, especially in the young universe.

Recent observations have found a quasar roughly 12 billion years in the past where the black hole seems to be growing at around 13 times this supposed speed limit while still shining brightly in X‑rays and launching a strong radio jet, something models didn’t expect.

These mechanisms help explain how you can end up with a black hole that outweighs tens of billions of Suns by today, especially in the densest galaxy clusters.

Why we say “biggest known” (and not absolute biggest)

When you see headlines like “biggest black hole ever found,” they always mean “biggest we’ve discovered so far given current data.” There are several reasons for this careful wording:

  • Observational limits: Distant or dust‑obscured black holes might be too faint or too tricky to measure with current telescopes.
  • Uncertain masses: Different measurement methods (stellar motions, gas dynamics, lensing, quasar light) don’t always agree perfectly, so quoted masses usually carry significant uncertainties.
  • Evolving universe: New surveys and telescopes (like the James Webb Space Telescope) keep revealing weirder and more extreme black holes, including runaway or ultra‑fast‑growing ones.

So, while Phoenix A’s black hole and TON 618 are leading candidates right now, astronomers fully expect that even bigger monsters may be hiding in the cosmic dark, waiting for future instruments and surveys to uncover them.

TL;DR:
Right now, the best candidate for the biggest black hole in the universe is the ultramassive black hole in the Phoenix A galaxy cluster, likely around 100 billion times the mass of the Sun, with TON 618 (≈66 billion Suns) as the most famous previous record‑holder—both almost certainly dwarfed by even bigger black holes we haven’t detected yet.

Information gathered from public forums or data available on the internet and portrayed here.