Inside Leiden University's largest research partnership: University of Amsterdam

Behind Leiden University's research output sits a defining relationship: 1,871 co-authored works with University of Amsterdam (Netherlands) in the five years to 2025, the university's single largest collaboration.

It anchors an unusually connected research base: 1,109 collaborating institutions across 79 countries, producing 33,223 joint works over the window, with international co-authors on 54% of output.

The collaborative work travels: its field-weighted citation impact stands at 3.82, where the world average is 1.0.

The Research Collaboration Index, the first global account of how universities actually collaborate, publishes its first full edition on Tuesday 15 September at 09:00 UK.

Every figure derives from the open global research record and is checkable at source.