Potassium (K) is an essential macronutrient for plant growth and development and influences yield and quality of agricultural crops. Maize (Zea mays) is one of the most widely distributed crops worldwide. In China, although maize consumes a large amount of K fertilizer, the K uptake/utilization efficiency (KUE) of maize cultivars is relatively low. Elucidation of KUE mechanisms and development of maize cultivars with higher KUE are needed. Maize KUE is determined by K⁺ uptake, transport, and remobilization, which depend on a variety of K⁺ channels and transporters. We review basic information about K⁺ channels and transporters in maize, their functions and regulation, and the roles of K⁺ in nitrogen transport, sugar transport, and salt tolerance. We discuss challenges and prospects for maize KUE improvement.