Intel, the market leader in microprocessors, denies wrongdoing.
Intel, the world's largest maker of semi-conductors, has been fined 26bn won ($25.4m; £13m) by South Korea's competition regulator.
The firm had offered rebates to South Korean computer companies and undercut competitor Advanced Micro Devices, the Korean Fair Trade Commission said.
Intel said that it was "disappointed" and disagreed with the findings.
It has been probed in several countries and in the European Union over claims it has abused its market position.
The Korean regulator said Intel must stop offering rebates to firms to encourage them not to use computers powered by chips made by rival AMD.
But Intel spokesman Nick Jacobs said the firm "did not use rebates in an anticompetitive fashion".
"To ask us to cease and desist behaviour which we are not and never have done is odd," he added.