Belt tensioning device for a belt drive, comprising: a base member which is firmly connectable to a stationary component; at least one tensioning arm, wherein a bearing assembly is provided between the base member and the tensioning arm, with which bearing assembly the tensioning arm is supported axially and pivotably about a pivot axis relative to the base member, wherein the tensioning arm has an opening for a drive part of a unit, which can extend into the opening in a mounted condition; a tensioning roller for tensioning the belt, which is mounted on the tensioning arm so as to be rotatable about an axis of rotation; a spring with which the tensioning arm is resiliently supported in circumferential direction; and a connecting assembly for connecting the tensioning arm to the base member, characterised in that the connecting assembly has at least two base member connecting portions (41, 41', 41") extending in the circumferential direction and at least two tensioning arm connecting portions (42, 42', 42") extending in the circumferential direction, which are connected to one another by an insertion and rotation movement; wherein a first contact face region is formed between a first base member connecting portion and a first tensioning arm connecting section, which is larger than a second contact face region formed between a second base member connecting portion (41', 41") and a second tensioning arm connecting portion (42', 42"); wherein the contact face regions formed between the base member connecting portions (41, 41', 41") and the tensioning arm connecting portions (42, 42', 42") form an axial bearing of the bearing assembly in the assembled state of the belt tensioning device. a base member which is firmly connectable to a stationary component; at least one tensioning arm, wherein a bearing assembly is provided between the base member and the tensioning arm, with which bearing assembly the tensioning arm is supported axially and pivotably about a pivot axis relative to the base member, wherein the tensioning arm has an opening for a drive part of a unit, which can extend into the opening in a mounted condition; a tensioning roller for tensioning the belt, which is mounted on the tensioning arm so as to be rotatable about an axis of rotation; a spring with which the tensioning arm is resiliently supported in circumferential direction; and a connecting assembly for connecting the tensioning arm to the base member, characterised in that the connecting assembly has at least two base member connecting portions (41, 41', 41") extending in the circumferential direction and at least two tensioning arm connecting portions (42, 42', 42") extending in the circumferential direction, which are connected to one another by an insertion and rotation movement; wherein a first contact face region is formed between a first base member connecting portion and a first tensioning arm connecting section, which is larger than a second contact face region formed between a second base member connecting portion (41', 41") and a second tensioning arm connecting portion (42', 42"); wherein the contact face regions formed between the base member connecting portions (41, 41', 41") and the tensioning arm connecting portions (42, 42', 42") form an axial bearing of the bearing assembly in the assembled state of the belt tensioning device.