Yes, a 19-year-old is considered a legal adult in almost every country and can travel independently both domestically and internationally. At 19, you are no longer subject to "unaccompanied minor" policies, which typically end at age 15 or 18 depending on the airline. However, there are a few practical "adult" hurdles to consider: many hotels in the United States and some in Europe require guests to be 21 or older to check in, and most car rental agencies will either deny service or charge a significant "Young Driver Surcharge" until you reach 25. While you can fly and cross borders with just your passport, it is wise to confirm that your specific accommodation allows 18+ check-ins. For international trips, ensuring you have comprehensive travel insurance is essential, as you will be responsible for your own logistics and medical emergencies.