An "ego-maniac" is someone who is very, very interested in themselves. They're proud of themselves and have high confidence. They may also like talking about themselves.

There are several words that are similar to "ego-maniac" but with slight differences:

• A conceited person is really proud of themselves, but maybe not as much as an "egomaniac". 
• A vain person is specifically very proud of how they look. (Same for "narcissist 
• A self-absorbed person is only interested in their own life and problems. However, being "self-absorbed" doesn't include as much confidence as being an "egomaniac".
• A selfish person takes things for themselves and doesn't think about other people's feelings.