An archaic title for a regional governor.
伯 (bó) here is the noble rank 'count/earl' (third of the Five Ranks
公侯伯子男 gōng-hóu-bó-zǐ-nán). The Han dynasty replaced the title with
州牧 (zhōumù) and
刺史 (cìshǐ), so
州伯 is mostly encountered in classical texts.