A planet carrier for a mechanical gearbox for a turbomachine includes a one-piece cage that extends about an axis of rotation defining an internal housing configured to receive a sun gear and planet gears of the gearbox. The planet carrier further includes a lubrication system with at least one bore formed in the cage and extending parallel to the axis over more than 30% of a maximum axial dimension (Lmax) of the cage. The lubrication system also includes for the at least one bore, at least two sprinklers which are fitted to the cage and which are each mounted in a recess of the cage.