In Person: 30 days before most elections. You may register in person on Election Day but only for Presidential elections
By Mail: 30 daysbefore Election Day.
Rhode Island General Law 17-1-3 allows an individual who has missed the voter registration deadline to register and vote for President/Vice-President only at their local Board of Canvassers on election day. This is only applicable for elections in which the office of President of the United States in on the ballot.
To register in Rhode Island you must:
be a citizen of the United States
be a resident of Rhode Island for 30 days preceding the next election
be 18 years old by Election Day
not be currently incarcerated in a correctional facility due to a felony conviction
not have been lawfully judged to be mentally incompetent
Local Election Office: This is the government office responsible for running elections in your region. Theses are the best people to contact if you have any questions at all about voting in your state.