Aeolian landforms are generally classified as having either depositional or erosional origins. Depositional landforms, which are sand sheets, ripples, and dunes of various types, are the most widespread type of aeolian landforms. To put it simply, dunes are the landforms that result from the deposition of sediment from a blowing wind–sand flux and result from the interaction between loose sediments and airflows. The most salient feature of dunes lies in their complexity and diversity in both their spatial scale and their morphology. The length of an individual dune can range from several meters to tens of kilometers, and their height can range from tens of centimeters to hundreds of meters. This chapter aims to introduce the morphological characteristics of different types of dunes on Mars.