TouchWiz is a discontinued user interface developed by Samsung Electronics with partners, featuring a full touch user interface. It is sometimes incorrectly referred to as an operating system. TouchWiz was used internally by Samsung for smartphones, feature phones, and tablet computers, and was not available for licensing by external parties. The Android version of TouchWiz also comes with the Samsung-made app store Galaxy Apps. It was replaced by Samsung Experience in 2017 with the release of Android 7.0 "Nougat".

Samsung's approach to its TouchWiz UI was distinct from its Android version updates. While Android updates brought new features and improvements to the operating system, Samsung often customized its UI separately. This meant that even if two devices ran the same Android version, their TouchWiz UI could differ based on the device's release date and hardware capabilities.

For example, the Galaxy S5, released with Android 4.4.2 KitKat, had a version of TouchWiz tailored to its hardware and design. When upgraded to Android Marshmallow, it retained an older version of TouchWiz UI with minor tweaks. On the other hand, the Galaxy S7, which launched with Android Marshmallow, featured a newer version of TouchWiz designed for its advanced hardware and features.

Samsung's strategy was likely aimed at optimizing the user experience for each device rather than standardizing the UI across all models. This approach allowed them to differentiate their devices and ensure compatibility with specific hardware configurations. However, it also led to inconsistencies in the user experience across devices running the same Android version.

The first, original edition of TouchWiz (version 1.0) was released in 2009. This 1.0 version was officially launched with the original Samsung Solstice in 2009.; although TouchWiz did first appear on the SGH-F480 Tocco in 2008. The last version of TouchWiz is TouchWiz Grace UX, which is on the Galaxy J1 mini prime LTE and the recalled Galaxy Note 7. TouchWiz Zero UX on the Galaxy J3 (2016) feature a more refined user interface as compared to the previous versions found on Samsung's older phones released prior to Galaxy S5's release. The status bar is now transparent during home screen mode in TouchWiz Nature UX 2.0 and TouchWiz Nature UX 2.5. In TouchWiz 4.0 on Galaxy S II and the Galaxy Note (both later updated to Nature UX), some of the features added include panning and tilt, which makes use of the accelerometer and gyroscope in the phone to detect motion.

TouchWiz is used by Samsung's own proprietary operating systems, Bada and REX, as well as by phones based on the Android operating system prior to Android 7. It is also present in phones running the Tizen operating system.

TouchWiz was succeeded by Samsung Experience in early 2017.

TouchWiz was a central issue in the lawsuit Apple Inc. v. Samsung Electronics.