Electrical muscle stimulation (EMS)—also known as functional electrical stimulation (FES)—has the potential to miniaturize haptic feedback technology and to integrate it into wearables and textiles. EMS offers a wide variety of haptic feedback, ranging from a small tingle to strong force feedback. In contrast to stationary force feedback systems and exoskeletons, EMS technology can easily be miniaturized as it does not require moving mechanical parts. Instead, EMS activates the user’s muscles. Textiles with embedded EMS technology offer the opportunity of ubiquitous haptic feedback. This kind of feedback is always available and can be applied to the whole body. In this chapter, we present the potential and limitations of EMS as a haptic feedback technology in wearable and textile-based computing. We begin with an in-depth literature review of haptic feedback and the design space of haptic feedback in general. Then, we describe the fundamentals of EMS, including typical placements of surface electrodes and specifics of textile EMS electrodes. This is followed by usage characteristics and safety issues of EMS feedback. Then, we present various application scenarios and introduce two research examples in depth, namely freehand interaction and pedestrian navigation with EMS feedback. Finally, we introduce a toolkit for haptic feedback prototyping and show how to apply it in different sample scenarios. We conclude this chapter with a discussion of research challenges and limitations, regarding EMS and textiles.