The present paper gives a technical revi ew of fracture toughness,and impact toughness for metallic materials in terms of the linear elastic fracture mechanics. This includes the early investigations and recent advances of fracture toughness test methods and practices developed by various agencies and societies. The review describes the most important fracture mechanics parameters:such as the elastic energy release rate G,the stress intensity factor K,the J - integral,the crack - tip opening displacement (CTOD) and the crack - tip opening angle (CTOA) from the basic concept,definition,to,tes t methods. Attention is paid to guidelines on how to choose an appropriate fracture parameter to characterize fracture toughness for the material of interest,and how to measure the fracture toughness value defined either at a critical point or in a resist ance curve format using laboratory specimens. The effects of loading rate,temperature and crack - tip constraint on fracture toughness as well as fracture instability analysis are also reviewed. https://www.ijiert.org/paper-details?paper_id=140338