The white lawnmower is adorned with the coat of arms of the Holy See.
In future, the employees of the Vatican Gardens will take care of its operation and maintenance.
These cover around 20 of the 44 hectares of the Vatican State, are located behind St Peter's Basilica and cover the Vatican Hill.
The grounds include administrative buildings, chapels, a railway station and a helipad.
Robert Prevost, Leo XIV since 8 May, has been the recipient of many gifts in recent months.
In October, he received a thoroughbred Arabian horse named Proton, and in September a motorbike.
This has now been auctioned off for 130,000 euros. The proceeds are intended for aid projects in Madagascar.