The closest Airports are located in:

For the journey within Germany train or car are recommended. The train connection is better for Berlin-Greifswald than for Hamburg-Greifswald. We recommend flying to Berlin Tegel airport and taking a train from Berlin to Greifswald.

From Rostock Airport, there is also a bus shuttle connection to Greifswald: http://flughafenshuttle-hgw.de/

For Train connections see: https://www.bahn.com/en/view/index.shtml

For an overview of the bus connection in Greifswald see: https://www.greifswald.info/wp-content/uploads/2016/07/Liniennetzplan_OEPNV_Greifswald.pdf

See also the website of the tourist information for directions: https://www.greifswald.info/service/anfahrt/