Bibliometrics focusses on the quantitative analyses of scholarly publication data. The method mostly means the application of output and impact indicators for research evaluation purposes. The increasing importance of bibliometrics for research evaluation can be observed since the mid-1980s—at least in the natural and life sciences. This overview of the literature on bibliometric indicators discusses methods for measuring output and impact in science. The main focus of the entry is on field-normalized citation impact indicators, which are in use for cross-time and cross-field comparisons of researchers, institutions, and countries. Besides field-normalized indicators, citation-based journal indicators (especially the well-known journal impact factor) and the h-index are addressed. The entry is of interest for many scientists and science policy analysts because research evaluation is prevalent in science and bibliometrics is at the core of research evaluation. It is additionally interesting for social sciences’ scientists because many methods used in bibliometrics are from social sciences’ disciplines.