The separation of powers principle and antitrust both relate to power and, notably, deal with the concentration of power. However, they are usually conceptualized, analyzed, and promoted separately. Separation of powers primarily refers to branches of government or to the main functions of the state and, in this respect, to public or state power or powers, while the economic power of private or, to a lesser extent, public firms is at the core of antitrust. Though appealing, this distinction is not clear-cut. These powers interact with one another. The concentration of politico-economic power in one or a few hands also raises fundamental issues in a democracy. Currently, and in the future, special attention must be given to the fact that a few digital platforms contribute to the digital infrastructure of democracy.