The phrase "domestic title" refers to winning a championship or being recognized as the best in a particular country or region. It is an achievement within one's own country, rather than on an international or global level. Full definition
Since the top 5 European leagues are widely considered to be most competitive we only take a look at domestic titles won in major European countries. (totalsportek.com)
And that was on the basis that they were returning the bulk of a squad that won an impressive domestic title just last spring. (footballdiscussion.net)
After 6 full seasons with Celtic, every major domestic title had been secured (some, a few times over). (pollemma.com)