I was wondering if a 2/0 wire will fit in a siemens 100 breaker?

Thanks for your help

You probably have a 100 Amp QP Frame, the largest wire it can handle is a #1/0.
See this spec sheet:
http://www.sea.siemens.com/SpeedFax0...x_01/01_32.pdf

Just had another question about this issue:
https://www.askmehelpdesk.com/electr...ker-41405.html