Yes, the Suica card can be used in Osaka and throughout most of Japan. While the Suica is a "Tokyo-region" card (issued by JR East), it is part of a nationwide interoperable system established years ago. This means your Suica (including the digital version on your iPhone or Apple Watch) works perfectly on all JR trains, private subways, and buses in the Kansai region, which includes Osaka, Kyoto, and Nara. You can also use it to pay at convenience stores, vending machines, and many restaurants in Osaka. The only major limitation in 2026 remains that you cannot use a Suica to tap through the gates for the Shinkansen (bullet train) unless it is specifically linked through the SmartEX app, nor can you "commute" between different IC regions (e.g., you can't tap in at Tokyo and tap out at Osaka). If you are starting your trip in Osaka, you would buy the local equivalent called the ICOCA card, but functionally, they are identical for almost all tourist needs across the country.