
My Canon landscape lens recommendations ...
Canon EF-S 10-22mm f/3.5-4.5 USM Lens
(EF-S mount only)
Canon EF-S 17-55mm f/2.8 IS USM Lens
(EF-S mount only)
Canon EF 17-40mm f/4.0 L USM Lens 
Canon EF 24-105mm f/4.0 L IS USM Lens 
Canon EF 70-200mm f/4.0 L IS USM Lens 
Canon EF 70-200mm f/4.0 L USM Lens 
Canon TS-E 17mm f/4 L Tilt-Shift Lens 
Canon TS-E 24mm f/3.5 L II Tilt-Shift Lens 
Canon EF 14mm f/2.8 L II USM Lens 
Canon EF 24mm f/1.4 L II USM Lens
Narrowing down the lenses to recommend for the landscape category is not easy.
Most lenses out there, from a 15mm fisheye to a 600mm Super Telephoto, can be used for landscape photography.
Many of the lenses in my General Purpose Lens Recommendations make excellent choices.
Value, versatility, image quality and physical attributes are the features I am looking for in a landscape lens.
Most landscape photography is done using small apertures for a desired large DOF (Depth of Field).
So, while landscape photography does not need the fastest (widest aperture) lens, it does need very good optics to capture the tiniest details.
The 17-40, 17-55, 24-105 and 70-200 f/4 lenses are not large or heavy (quite portable),
but are built solidly enough to take the bumps and bruises encountered when hiking the landscape.
Take pair of zooms along to be able to cover the wide through telephoto opportunities.
All listed lenses are about best-in-their-class for optic quality.
If image stabilization is not wanted/required, the 17-40 f/4 and 70-200 f/4 make a great and attractively-priced combo.
While they are not as affordable as the other recommended lenses, the
Canon EF-S 17-55mm f/2.8 IS USM Lens,
Canon EF 24-105mm f/4.0 L IS USM Lens and
Canon EF 70-200mm f/4.0 L IS USM Lens
have image stabilization in their feature list.
Unless your landscape subjects are moving (wind can cause this), image stabilization can make the difference between getting the shot
and getting a blurry picture in those times a tripod is not available or wanted.
I included some Canon prime lenses in the landscape recommendation list.
While these lenses do not have the focal length versatility of the Canon zoom lenses, they offer superb image quality.
If you have the time to manually focus your shot and adjust movements, the Canon TS-E 17mm f/4 L Tilt-Shift Lens
Canon TS-E 24mm f/3.5 L II Tilt-Shift Lens will give you amazing image quality right into full frame corners.
Their movements will give you even more control - especially control over the placement of the focus plane.
The Canon EF 14mm f/2.8 L II USM Lens and
Canon EF 24mm f/1.4 L II USM Lens will give you great optics in a great package - with AF.
As always, read the full reviews to see which lens(es) are best for you.