Alkyne metathesis catalyzed by metal alkylidynes is a powerful method for forming a triple bond. Among different modes of alkyne metathesis, cross-metathesis and ring-closing metathesis are frequently employed in the synthesis of natural products; homo-metathesis and ring-opening metathesis are harnessed in the preparation of cyclooligomeric and polymeric structures. The scope and utility of this reaction has been significantly expanded by the development of highly active, functional-group-tolerant, and user-friendly catalysts. In this Chapter, various aspects of alkyne metathesis are described in detail, including mechanism and applications in natural product synthesis. The Tables provide extensive examples of alkyne metathesis reactions and are organized in the following order: homo-metathesis, cross-metathesis, ring-closing metathesis, cyclooligomerization, polymerization, and depolymerization–cyclooligomerization.