Transition metal dichalcogenides are among the most studied 2D nanomaterials. This family of materials with a general formula of MX₂ (M = transition metal, X = S, Se or Te) is represented by approximately 60 members covering metallic conductors, semiconductors, topological insulators as well as superconductors or Weyl semimetals. Due to their layered structure, they can be easily exfoliated down to single layers which results in dramatic changes in their chemical and physical properties. With their broad range of interesting properties, they find applications in various fields including electronics, optoelectronics, sensing or catalysis. In this chapter, we first provide an overview of their properties. We then move on to provide a summary of the most common synthetic routes. The final part of this chapter is devoted to applications of TMDs.