Yes, a day trip from Lisbon to Porto is entirely doable in 2026, primarily thanks to the high-speed Alfa Pendular and Intercidades trains operated by CP (Comboios de Portugal). The journey from Lisboa Oriente to Porto Campanhã takes approximately 2 hours and 40 minutes each way. By taking an early 7:00 AM train, you can arrive in Porto before 10:00 AM, leaving you with about 8 to 10 hours to explore the Ribeira district, visit a Port wine cellar, and walk across the Dom Luís I Bridge before catching a 7:00 PM or 8:00 PM return train. While a car drive takes about 3 hours and buses take roughly 3 hours and 15 minutes, the train is the "best" option to maximize your time in the city without the stress of traffic. It is a long day with about 5-6 hours of total travel time, but for those with limited time in Portugal, it provides a perfect "highlight reel" of the country's second-largest city and its stunning Douro River views.