It is the members of the IOC, meeting at their Session, who choose the host city. Electing the host city for the Olympic Games is one of the powers of the Session.
The host city is elected by a majority of the votes cast by secret ballot. Each active member has one vote. The members who are nationals of the countries with a Candidate City are not allowed to vote when their city remains in contention.
The honorary members, honour members and suspended members are not allowed to vote. If a majority is not achieved in the first round of voting, the Candidate City with the fewest votes is eliminated, and a further round or rounds of voting are held until a majority is obtained by one city.