An agitator configured to be installed in a tank, the agitator comprising a drive arrangement, an agitator shaft being provided with agitator blades and being configured to extend downwardly from the drive arrangement along a shaft axis and to be rotated about the shaft axis by the drive arrangement, and a shaft support for supporting a lower portion of the rotatable shaft, the shaft support comprising: a support ring extending around a central geometrical axis and being configured to circumscribe the lower portion of the rotatable shaft, the support ring having an inwardly facing bearing surface configured to form a slide bearing journaling the lower portion of the rotatable shaft, characterized in that the bearing surface has a non-circular shape, as seen in a projection in a plane having a normal parallel to the shaft axis, in the sense that a first distance (d 1), which is measured in a first direction in the plane and which forms a longest distance between the bearing surface and a circle representing an outer envelope surface (2a, 10) of the shaft is larger than a second distance (d 2), which is measured in a second direction in the plane and which forms a shortest distance between the bearing surface and the circle representing the outer envelope surface (2a, 10) of the shaft, wherein the second distance (d 2) is less than 70% of the first distance (d 1). a drive arrangement, an agitator shaft being provided with agitator blades and being configured to extend downwardly from the drive arrangement along a shaft axis and to be rotated about the shaft axis by the drive arrangement, and a shaft support for supporting a lower portion of the rotatable shaft, the shaft support comprising: a support ring extending around a central geometrical axis and being configured to circumscribe the lower portion of the rotatable shaft, the support ring having an inwardly facing bearing surface configured to form a slide bearing journaling the lower portion of the rotatable shaft, characterized in that the bearing surface has a non-circular shape, as seen in a projection in a plane having a normal parallel to the shaft axis, in the sense that a first distance (d 1), which is measured in a first direction in the plane and which forms a longest distance between the bearing surface and a circle representing an outer envelope surface (2a, 10) of the shaft is larger than a second distance (d 2), which is measured in a second direction in the plane and which forms a shortest distance between the bearing surface and the circle representing the outer envelope surface (2a, 10) of the shaft, wherein the second distance (d 2) is less than 70% of the first distance (d 1). a support ring extending around a central geometrical axis and being configured to circumscribe the lower portion of the rotatable shaft, the support ring having an inwardly facing bearing surface configured to form a slide bearing journaling the lower portion of the rotatable shaft, characterized in that the bearing surface has a non-circular shape, as seen in a projection in a plane having a normal parallel to the shaft axis, in the sense that a first distance (d 1), which is measured in a first direction in the plane and which forms a longest distance between the bearing surface and a circle representing an outer envelope surface (2a, 10) of the shaft is larger than a second distance (d 2), which is measured in a second direction in the plane and which forms a shortest distance between the bearing surface and the circle representing the outer envelope surface (2a, 10) of the shaft, wherein the second distance (d 2) is less than 70% of the first distance (d 1).