The Samsung Galaxy S4 is an Android smartphone produced by Samsung Electronics as the fourth smartphone of the Samsung Galaxy S series and was first shown publicly on March 14, 2013, at Samsung Mobile Unpacked in New York City. It is the successor to the Galaxy S III, which maintains a similar design, but with upgraded hardware, more sensors, and an increased focus on software features that take advantage of its hardware capabilities—such as the ability to detect when a finger is hovered over the screen, and expanded eye tracking functionality, it was released the previous year. A hardware variant of the S4 became the first smartphone to support the emerging LTE Advanced mobile network standard. The T-Mobile version of the Galaxy S4, named the model (SGH-M919), was released the same month. The phone's successor, the Samsung Galaxy S5, was released the next year.

Android is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets. Android is developed by a consortium of developers known as the Open Handset Alliance, though its most widely used version is primarily developed by Google. It was unveiled in November 2007, with the first commercial Android device, the HTC Dream, being launched in September 2008.