Earth-affecting solar transients encompass a broad range of phenomena, including major solar flares, CMEs, ICMEs, solar energetic particle events, and corotating interaction regions.?In the past decade, nearly continuous observations of the Sun and the inner heliosphere with an unprecedented wide spatial coverage from a fleet of spacecraft, including STEREO Ahead/Behind, SDO, SOHO, Messenger, Venus Express, ACE and WIND, in combination with a significant advancement of global MHD numerical simulation and theoretical analysis, have greatly improved our understanding of solar transients and the prediction of their potential impact on Earth. This Topical Collection is based on the International Study of Earth-affecting Solar Transients (ISEST) project, initially launched in 2013 to bring together scientists from many countries to join efforts on studying solar transients. ISEST became one of the four research projects of the Variability of the Sun and Its Terrestrial Impact (VarSITI) program, sponsored by the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) for the period of 2014 – 2018. Originally published in the journal Solar Physics, volumes 292 (2017) and 293 (2018).