Most cafés and accommodations offer free WiFi; however, it’s still a good idea to have your own connection. After trying different providers, I found Vodafone to be the most reliable. At the airport, there is a Vodafone kiosk where you can buy a physical SIM (usually more expensive than e-sim. Last time it was unlimited data for €20 for 20 days) or an eSIM. Note: prices could change.
The best deal (as of March, 2026) I’ve found so far was purchasing an eSIM (Vodafone) through the TAP Air Portugal app, which was around €15 for 30 days.
MEO is good for rural areas and road trips.
NOS is best in the big cities like Lisbon, Porto, Coimbra, etc.
Please note that the U.S.-based companies, such as Verizon, AT&T, and even T-Mobile, are not good choices for mobile data use in Portugal. Service is typically expensive and may offer slower connections with frequent interruptions.