No, a 17-year-old cannot sail alone on a Royal Caribbean cruise. The cruise line has a strict age policy regarding unaccompanied minors. For cruises departing from North America, the minimum age to sail unaccompanied is 21. For cruises departing from Europe, South America, Asia, or Australia, the minimum age is 18. In both scenarios, a 17-year-old is considered a minor and must be accompanied in the same stateroom by an adult who meets the age requirement (either 18 or 21 depending on the port). There is an exception if the 17-year-old is staying in a connecting stateroom with their parents or legal guardians, but they cannot be on the ship without a designated adult supervisor officially listed on their reservation. This policy is strictly enforced at embarkation to ensure the safety and legal responsibility of younger guests. If a 17-year-old attempts to board without a qualifying adult, they will be denied boarding without a refund. Additionally, even if they are with an adult, they are subject to the ship's curfew and cannot consume alcohol or gamble in the casino.