From Byrne's 1923 Dictionary of The English Law:
"The person who grants the lease is called the lessor; the person to whom it is granted being the lessee."
In most cases, the lessor would be the owner. When the thing being leased is land or some other real property, such as a flat, an apartment or some other residential premises, the lessor is often referred to as the landlord.
The term is most populraly used within the context of residential tenancy as in this example from the Prince Edward Island's residential tenancy statute:
"Lessor means the owner or other person permitting the lessor occupation, pursuant to a rental agreement, of residential premises and includes his heirs, assigns, personal representatives and successors in title."
In French, locateur or bailleur.
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