The Luzhniki, which has a 90,000 capacity, will also stage the opening match and a semi-final following approval by FIFA's executive committee. St Petersburg will stage the other semi-final.
Moscow, St Petersburg, Kazan and Sochi were approved as venues for the 2017 Confederations Cup, also to be held in Russia, FIFA said.
In a separate decision, Kosovo, which is not a FIFA member, was given permission to play friendly matches at "youth, amateur, women's and club football" level.
However, no mention was made of a decision on Kosovo playing friendly internationals at senior level against FIFA member nations.
FIFA had agreed in principle to allow Kosovo to play friendlies last May but, following opposition from Serbia and UEFA president Michel Platini, has delayed implementation of the ruling.
The delays have angered the Football Federation of Kosovo (FFK) which says it is only seeking the right to play friendly internationals, not become members of FIFA.
Kosovo declared independence from Serbia in 2008 but has not yet won recognition from the United Nations.
FIFA and UEFA statutes state that only nations recognised by the UN can be accepted as members.
Moscow's Luzhniki uses an artificial pitch because of the frigid Russian winters although a natural pitch was laid for the 2008 Champions League final, staged at the stadium.
Eleven Russian cities will host the 2018 World Cup with Moscow having two venues. The other cities are St Petersburg, Kaliningrad, Nizhny Novgorod, Kazan, Samara, Volgograd, Rostov, Sochi, Saransk and Yekaterinburg. (Writing by Brian Homewood in Berne; Editing by Clare Fallon)
- Sports & Recreation