Use of lean or ultra-lean air-fuel ratios is an efficient and proven strategy to reduce fuel consumption and pollutant emissions. Previous works indicate that lean burn mixtures improves engine thermal efficiency by improving combustion quality, reducing heat transfer losses and increasing the possibility of apply higher compression ratios. However, lower fuel concentration in cylinder hinders mixture ignition, requiring greater energy to start combustion. To favor the ignition process, several high energy providers methods have been studied. Between them, prechamber ignition system presents potential reductions in emission levels and fuel consumption, operating with lean burn mixtures and expressive combustion stability. In this paper, a literature review has been made about prechamber ignition systems as lean combustion technology, focusing in the several investigations regarding combustion and emissions characteristics and presenting the key advantages and challenges in prechamber ignition technology application. From this review can be observed that the pre-chamber ignition system is an important way to increase thermal efficiency, reduce fuel consumption and emissions in spark ignition engines.