Police figures show that there were deadly accidents involving motorcyclists in at least six German states.
Two bikers were killed in each of Bavaria, North Rhine-Westphalia and Lower Saxony, while Brandenburg, Rhineland-Palatinate and Saxony each saw one biker die on their roads.
The causes of most of the accidents are not yet clear.
Good weather that blessed the weekend is unlikely to continue into the week, the German Weather Service (DWD) reports.
Showers and storms are likely throughout the remainder of the week, especially in the north and west of the country.