Four-time champions Italy missed out on qualification for the first time since 1958 after losing in the playoffs to Sweden, while the Netherlands failed to qualify for the tournament for the first time since 2002 after finishing third in 2014, and second in 2010. Iceland, with 335,000 inhabitants, became the smallest country ever to qualify for the World Cup finals.
Apart from Russia, which qualified automatically as hosts, all remaining 52 FIFA-affiliated national teams from UEFA at the registration deadline of January 2015 entered qualification.
Gibraltar, despite being a UEFA member since 2013, was not a FIFA member at the time of the registration deadline, and thus was not eligible to enter qualification for the FIFA World Cup. They appealed to the Court of Arbitration for Sport to challenge FIFA's refusal to grant membership in order to enter World Cup qualifying. In May 2016, the CAS found in Gibraltar's favour and ordered that FIFA put Gibraltar forward for FIFA membership, which would permit Gibraltar to take part in the qualifiers if membership was granted.
Kosovo became a UEFA member on 3 May 2016, and together with Gibraltar, applied for membership in the FIFA Congress in 12–13 May 2016. FIFA confirmed that in the case both associations succeeded in becoming a member, they would be entitled to participate in the 2018 FIFA World Cup qualifiers, with UEFA tasked to integrate them into the competition.
On 13 May 2016, both Kosovo and Gibraltar were officially admitted as FIFA members, thus allowing them to compete. UEFA created a task force to discuss how to integrate the two teams into the competition, and on 9 June 2016 UEFA announced that Kosovo would be assigned to Group I, to avoid meeting Bosnia and Herzegovina for security reasons, and Gibraltar would play in Group H.
The qualification structure was as follows:
First round (group stage): The 54 teams were divided into nine groups of six teams each to play home-and-away round-robin matches. The winners of each group qualified for the 2018 FIFA World Cup, and the eight best runners-up advanced to the second round (play-offs).
Second round (play-offs): The eight best runners-up from the first round played against one other team over two legs, home and away. The draw for these matches was held on 17 October 2017. The first legs were played on 9–11 November, and the second legs were played on 12–14 November 2017. The winners of each tie qualified for the 2018 FIFA World Cup.
Qualifying matches started in September 2016, following UEFA Euro 2016, and finished in November 2017.
The draw for the first round (group stage) was held as part of the 2018 FIFA World Cup Preliminary Draw on 25 July 2015, starting 18:00 MSK (UTC+3), at the Konstantinovsky Palace in Strelna, Saint Petersburg, Russia.
The seeding was based on the FIFA World Rankings of July 2015. The 52 teams were seeded into six pots:
Pot 1 contains the teams ranked 1–9.
Pot 2 contains the teams ranked 10–18.
Pot 3 contains the teams ranked 19–27.
Pot 4 contains the teams ranked 28–36.
Pot 5 contains the teams ranked 37–45.
Pot 6 contains the teams ranked 46–52.
Each six-team group contained one team from each of the six pots, while each five-team group contained one team from each of the first five pots.
Due to the centralisation of media rights for European qualifiers, England, France, Germany, Italy, Spain and the Netherlands were all drawn into six-team groups. Netherlands and France were drawn together in Group A, and Spain and Italy were drawn together in Group G.
In consideration of the delicate political situations of the relationships between Armenia and Azerbaijan, UEFA requested that FIFA maintain the current UEFA policy not to draw these teams into the same qualification groups (since the two teams were in the same seeding pot, this would not have happened regardless of the request).
Teams were allocated to seeding pots as follows (July 2015 FIFA Rankings shown in second column; the national teams which eventually qualified for the final tournament are presented in bold; the national teams who took part in the play-offs are presented in italic).
The hosts Russia were to be partnered with five-team Group H for friendlies. However, with the admission of Kosovo and Gibraltar, all groups were filled to contain six teams and the Russia friendlies against Group H teams were cancelled. UEFA vice-president Hryhoriy Surkis said that the UEFA management would deal with the issue of finding opponents for Russia to play friendlies.
When the draw was made groups H and I had one team fewer than the other groups so it was decided that matches against the last-placed team in each of the six-team groups would not be included in the ranking of the second-placed teams. Even after the admission of Kosovo and Gibraltar, and with all groups now containing six teams, this rule did not change and matches against the sixth-placed team in all groups were still discarded. As a result, only eight matches played by each team were counted in the second-placed table.
The eight best runners-up were determined by the following parameters, in this order:
Source: FIFA Rules for classification: Counting only matches against teams ranked first to fifth in the group, 1) Points; 2) Goal difference; 3) Goals scored; 4) Fair play points; 5) Drawing of lots.
The draw for the second round (play-offs) was held on 17 October 2017, 14:00 CEST (UTC+2), at the FIFA headquarters in Zürich, Switzerland. The eight teams were seeded by FIFA World Rankings published on 16 October 2017, rather than qualifying record, with the top four teams in Pot 1, and the remaining four teams in Pot 2. It so happened that the top four teams by qualifying record were the same as the top four by FIFA World Ranking. Teams from Pot 1 played teams from Pot 2 on a home and away basis, with the order of legs decided by draw.
UEFA unveiled the branding for the qualifiers on 15 April 2013. It shows a national jersey inside a heart, and represents Europe, honour and ambition. The same branding was also used for the European qualifiers for the UEFA Euro 2016.