This chapter provides an introduction to radio-frequency identification (RFID) and positioning techniques tailored to RFID. The discussion unfolds by elucidating the fundamental characteristics of RFID readers and tags, with a particular focus on key wireless solutions for passive identification. Special attention is devoted to the distinctive aspects of ultra-high frequency (UHF) RFID, highlighting the electronic product code (EPC) Class 1/Generation2 protocol. The chapter delves into positioning techniques specifically tailored for UHF RFID applications. The main signal features that can be exploited for positioning of UHF RFID tags are considered, in particular, the received signal strength indicator (RSSI) and the signal phase. Techniques leveraging fingerprints are introduced. The exploitation of the signal phase, by adopting multiple antennas, is considered both in far-field scenarios (thus enabling angle-of-arrival (AoA) estimation with antenna arrays) and near-field scenarios, by employing large apertures. For each technique, the main characteristics and practical limitations within operational environments are discussed.