The International Colloquium Stability and Ductility of Steel Structures. 11 - 13 September 2019, Faculty of Civil Engineering CTU in Prague, Czech Republic. The series of International Colloquia on Stability and Ductility of Steel Structures have been supported by the Structural Stability Research Council (SSRC) for more than forty years and its objective is to present the progress in theoretical, numerical and experimental research in the field of stability and ductility of steel and steel-concrete composite structures. Special emphasis is laid on new concepts and procedures concerning the analysis and design of steel structures and on the background, development and application of rules and recommendations either appearing in recently published Codes or Specifications or about to be included in their upcoming versions. This International Colloquium series started in 1972 in Paris and its subsequent editions took place in different cities with the last five being held in: Timisoara, Romania (1999), Budapest, Hungary (2002), Lisbon, Portugal (2006), Rio de Janeiro, Brazil (2010) and Timisoara, Romania (2016).