The 49th edition of the International Physics Olympiad (IPhO2018) took place in Lisbon, from 21 to 29 July. The IPhO is an annual competition in physics for secondary school students, aiming at promoting physics and the development of international contacts in physics education, involving individual theoretical and experimental exams. The IPhO began in Warsaw, Poland, in 1967, with 5 participating countries. Since then, IPhO has grown to worldwide coverage and this year 396 competitors from 86 countries attended the competition in Lisbon, organised by the Portuguese Physical Society on behalf of the Portuguese Ministry of Education.