Market leader
 

 

The firm or company which has the biggest share of the available market for a specified product. The phrase is normally used in the context of sales in one country. e.g. the market leader for product B in the U.K. may be an American or German company which, in its home market, is merely another competitor ranked no higher than an 'also ran'.

Reference: The Penguin Business Dictionary , 3rd edt.