It also awarded the 2019 women's World Cup to France which defeated South Korea in a vote by the Fifa executive committee.
The decision on the date of the 2022 final ended a long-running and acrimonious debate about the timing. A change to a winter World Cup was forced on Fifa by the scorching temperatures in Qatar in June-July.
European clubs have complained about the disruption to their cash-rich domestic championships, however.
And even the dates for the November-December tournament were not unanimous.
England and other countries opposed this because of the clash with traditional games played over the Christmas and New Year period.
UEFA, Europe's governing body had initially preferred December 23rd for the final, but have since changed their minds. European federations are still worried about dates for international matches scheduled at that time, however.
The compromise will probably see the tournament reduced to 28 days instead of the 32 for the 2014 World Cup in Brazil.
Fifa's communications chief Walter de Gregorio said that deciding the date of the final was "an important step. Finally we know and we can move forward".
An end to uncertainty
"The final will be on December 18th. It is a Sunday and it is also the national day of Qatar, so it fits perfectly," de Gregorio told reporters.
"In principle we try to play in 28 days. The next step will be to have different talks, especially (on) the international calendar," the official added.
The date of the start of the tournament will probably not be decided until the end of the year, FIFA sources said.
Noel Le Graet, president of the French Football Federation, said the proposed date could push European leagues to play more matches in summer.
"It is a good decision for players," Le Graet told reporters. "I have always been a supporter of playing less in winter and more in summer."
European clubs are expected to press for some kind of compensation for halting their national league and Champions League games for at least five weeks.
Blatter has previously said that compensation was not needed. But he has since held talks with the head of the European Club Association, Karl-Heinz Rummenigge, chairman of German giants Bayern Munich.
Fifa paid $70 million to clubs who had players at the 2014 World Cup and this scheme could be enlarged for 2022.
UEFA is already promising 150 million euros ($170 million) for clubs whose players are on duty at the 2016 European Championships in France.
France will also hold the 2019 women's World Cup, which is fast growing in popularity around the globe, and the women's under 20 World Cup in 2018.
Blatter said that France and South Korea had both been strong candidates for the World Cup but the final vote was made by the executive committee "with confidence".
Blatter hailed France's attempts to develop the women's game.
France's national team are ranked third in the world and Lyon have been European club champions twice in the past four years.
"It is magnificent news for French women's football," said Lyon player Camille Abily.
This year's women's World Cup will be held in Canada and huge crowds are expected for the tournament spread across six cities from June 6th to July 5th.
France has already decided it will stage the World Cup in nine cities.