Primary sources can be different things in different fields. 

In History

A primary source in history is generally a first-hand account or artifact from an event or time period.  Here is a full definition from the American Library Association:

"Primary sources are the evidence of history, original records or objects created by participants or observers at the time historical events occurred or even well after events, as in memoirs and oral histories. Primary sources may include but are not limited to: letters, manuscripts, diaries, journals, newspapers, maps, speeches, interviews, documents produced by government agencies, photographs, audio or video recordings, born-digital items (e.g. emails), research data, and objects or artifacts (such as works of art or ancient roads, buildings, tools, and weapons). These sources serve as the raw materials historians use to interpret and analyze the past. "

--American Library Association, Primary Sources on the Web: Finding, Evaluating, Using

In the Libraries' Databases A-Z are many resources of the type "primary source."  See a link to the list below.  

Not all primary sources are online, however,  Manuscript collections, published books from the time period, magazine and newspaper articles could also be primary sources.  Explore archival materials in our Special Collections or Ask Us for help in identifying manuscript collections for your research topic. 

In Education, Social Sciences, and Sciences

In education and sciences fields you might be asked to find examples of primary research or original research. These tend to be scholarly articles reporting on original research conducted by the authors.  Unlike less formal reviews or editorials or news articles, these articles will usually include a research question, a literature review, a research methodology, and discussion of findings. 

In OneSearch and other databases, use the filters for peer-reviewed and the articles material type to filter down your results.  Then, review the article abstracts and text to verify that this is a first-hand account of the results of research.

 See more tips in our FAQ on primary sources in the sciences.