Transparent heaters (THs) are widely used for various applications, such as in smart windows, deicers, defoggers, displays, and thermotherapy pads. The rapid development of flexible electronics has led to a demand for flexible and even stretchable THs. At present, most stretchable THs are designed using a combination of electronically conductive networks and flexible polymer materials. Electronic THs still face common challenges, such as a transparency-conductance trade-off, non-uniform heating, and poor interfacial adhesion. In this work, an ionic TH is reported based on a stretchable and transparent ionogel. Joule heating from an ionic current induced by alternating voltage functions as the heating source. This ionogel-based TH exhibits excellent and steady mechanical, optical, electrical, and thermal properties, simultaneously solving the abovementioned three problems relating to electronic THs. Two simple applications of this ionogel-based TH are demonstrated: deicing and boiling water. This reported ionogel-based TH provides a new material choice and heating principle to compete with conventional electronic TH technology.