It's a bit more complicated in Germany ;-) Basically: Senators are called "Abgeordnete" and we translate that into "Members of Parliament" or simply "MPs" [for instance, members of the European Parliament are also abbreviated with "MEPs").
But: Germany consists of 16 states, but 3 of them (Berlin, Hamburg and Bremen) are city states. The state governments of the states Bavaria, Saxony and Thuringia are called "Staatsregierung", it's called "Ministerrat" in Rhineland-Palatinate and Baden-Württemberg and "Senat" in Berlin, Bremen and Hamburg. The head of every government except for the governments of the city states is indeed called a "Ministerpräsident", but the heads of the governments of Bremen, Hamburg and Berlin are called "Präsident des Senats" ("President of the senate"). And since the "Präsident des Senats" is also the mayor of his city, you call
- the "Ministerpräsidenten" of Berlin, Hamburg and Bremen "governing mayors of Berlin, Hamburg and Bremen - Regierender Bürgermeister" and
- the "Ministerpräsidenten" of the remaining 13 states "Ministerpräsident des Landes...". Since all MPs of Berlin, Hamburg and Bremen (including the "Ministerpräsident") are also called "Senatoren/senators" because of the name of its Parliament ("Senat"), the "Ministerpräsident" can be called a "senator" in this particular case.
Sorry for the confusion, but I hope you got the idea why it's not easy to decide how you translate these words into German due to the different political systems =)
Hope this does not confuse you too much =)