The phrase "dominant provider" is correct and usable in written English.
You can use it to refer to a company or individual that has the most significant market share or presence in a particular industry. For example, "Microsoft is the dominant provider of personal computer operating systems."
Beneficiaries who filled opioid prescriptions from two providers had an average of 5.56 prescriptions (95% confidence interval 5.54 to 5.58) provided by the dominant provider and 1.57 (1.57 to 1.58) prescriptions provided by the second most dominant provider.
The proportion of total prescriptions provided by a single dominant provider declined as beneficiaries received prescriptions from multiple providers (table 2).
Markit is the dominant provider of pricing information in the derivatives industry, providing the data to more than 300 financial firms that use it to determine the prices of similar contracts on their own books.
Microsoft's greatest strength is its enormous resources as the dominant provider of computer operating systems.
In much of the country, cable is the dominant provider of very-fast broadband Internet service.
But AOL, as the dominant provider of consumer Internet access, has advantages few other software companies can exert.
AWS hosts operational software, data, and processing for millions of other enterprises, making it the dominant provider.
The dominant provider is moving away from the new entrant's offerings and toward a more profitable segment of the market.
It could soon dethrone the local cable-TV firm as the dominant provider of pay-TV services.
American Express is a dominant provider of the charge cards that are favored by many corporations and affluent individuals.
These markets are a dominant provider of mortgage finance and an important source of car loans and consumer credit.
