at least 12,600 trillion or more. For now, it is unknown.
If you counted 1 intelligent alien civilization per second, it would take 400 million years to count all 12,600 trillion intelligent alien civilizations in the universe.
There are no known alien civilizations in our universe.
There are over 10,000 trillion alien races/civilizations (100,000+ per galaxy; excluding humans) in the Outlaw Star Universe.
There are over 10,000 trillion alien races/civilizations (100,000+ per galaxy; excluding humans) in the Code Lyoko Universe.
There are over 10,000 trillion alien races/civilizations (100,000+ per galaxy; excluding humans) in the Titan AE Universe.
There is absolutely know way of knowing. So far we only intelligent civilization that we know of is our own. We have no idea of how common life is in the universe, let alone intelligent life. The number is probably too high for the observable universe. If there are 12.6 quadrillion civilizations in the observable universe of 100 billion galaxies, that gives us an average of 126,000 civilizations for an average galaxy. Since our galaxy has more stars than most that would suggest that there are several hundred thousand civilizations in the Milky Way, perhaps over a million. Suggesting so many civilizations exist in our galaxy would invoke the question of Fermi's paradox: where is everybody?
There are over 10,000 trillion alien races/civilizations (100,000+ per galaxy; excluding humans) in the Damocles Universe (the universe Sigma, the qeelocke, Damocles, the Sword, and One-Eyed Jack's crew originated in).
There are over 10,000 trillion alien races/civilizations (with 100,000+ per galaxy; excluding humans) in the Animorphs universe.
It is currently not known whether humans are the only intelligent race in existence. While intelligent life may be relatively rare in the universe, there is no evidence to suggest that it is unique to Earth. In fact, there are many theories and speculations about the potential for intelligent life on other planets, and some scientists believe that it is likely that there are other intelligent civilizations out there. As for why humans may feel lonely in such a massive universe, there are many possible reasons. Some people may feel a sense of isolation and disconnection from the universe due to their limited understanding of its vastness and complexity. Additionally, the fact that humans have not yet made contact with any other intelligent civilizations may contribute to a feeling of loneliness. Finally, the vastness of the universe can be overwhelming and can make individuals feel small and insignificant in comparison. Overall, there are many reasons why humans may feel lonely in the universe, and these reasons are likely to vary from person to person.
There are trillions of alien races (excluding humans) in the WildStorm Universe.
There are over 10,000 trillion alien races (100,000+ per galaxy; excluding humans) in the Deadman Wonderland Universe.
There are no alien races in Cowboy Bebop (But in the Cowboy Bebop universe, and fan-fiction also; there are trillions of them (with hundreds of thousands of them in each galaxy)).