Today's multimedia search engines are expected to respond to queries reflecting a wide variety of information needs from users with different goals. The topical dimension (“what” the user is searching for) of these information needs is well studied; however, the intent dimension (“why” the user is searching) has received relatively less attention. Specifically, intent is the “immediate reason, purpose, or goal” that motivates a user to query a search engine. We present a thorough survey of multimedia information retrieval research directed at the problem of enabling search engines to respond to user intent. The survey begins by defining intent, including a differentiation from related, often-confused concepts. It then presents the key conceptual models of search intent. The core is an overview of intent-aware approaches that operate at each stage of the multimedia search engine pipeline (i.e., indexing, query processing, ranking). We discuss intent in conventional text-based search wherever it provides insight into multimedia search intent or intent-aware approaches. Finally, we identify and discuss the most important future challenges for intent-aware multimedia search engines. Facing these challenges will allow multimedia information retrieval to recognize and respond to user intent and, as a result, fully satisfy the information needs of users.