This book is written based on the authors' research results in the field of titanium microalloying technology over the years.It aims at introducing this field to the students and technicians in need.This book consists of six chapters.Chapter 1 introduces the definition, role, development history, and technical and economic characteristics of titanium microalloyed steel.Chapter 2 systematically discusses the principles of chemical metallurgy of titanium microalloyed steel.It contains the thermodynamics of titanium in molten steel, the reaction between titanium-bearing molten steel and slags and refractories, and the principles of oxide inclusion control technology.Chapters 3 and 4 discuss the physical metallurgy of titanium microalloyed steel.Chapter 3 focuses on the dissolving and precipitation of titanium-bearing phases, and Chap.4 focuses on the recrystallization and phase transformation.Chapter 5 summarizes the technology of controlling production,structure and performance of titanium microalloyed steel.Chapter 6 introduces the development and application of representative titanium microalloyed steel products.This book is translated from the Chinese version of Titanium Microalloyed Steel, which was published by Metallurgical Industry Press in 2016.In this English version, Chap.6 of the original Chinese version was revised by appending the application of titanium microalloying technology in the development of auto-mobile beam steel, enamel steel and yoke steel.