Dithmar Blefken was a German preacher and minor 17th century geographer.
[1] Blefken is known for Islandia (complete name Islandia, sive Populorum & mirabilium quae in ea Insula reperiuntur accuratior descriptio), a description of Iceland published first in 1607 in Leiden.
He claimed it to be based on his journey to the island while accompanying merchants from Hamburg; this is, however, not certain.
Arngrímur Jónsson, a contemporary Icelandic scholar, was a fierce critic of Blefken's work (as well as of other authors).
[2] Although the book contained many inaccuracies it was quite influential at the time, especially in northern parts of Europe.