Moscow - Six teams have already qualified for the Round of 16, leaving 10 remaining spots up for grabs.
Here's what teams in Group A and Group B need to do to keep their 2018 Soccer World Cup hopes alive.
QUIZ: Can you name all the semi-finalists in all the previous Soccer World Cups?
GROUP A
Group A is pretty simple. Russia and Uruguay have clinched berths in the Round of 16 and play each other Monday to determine who wins the group. Egypt and Saudi Arabia have been eliminated.
Russia have a superior goal difference so Uruguay would need all three points to top the group.
Remaining fixtures on Monday:
Uruguay v Russia - 16:00
Saudi Arabia v Egypt - 16:00
GROUP B
Morocco have been eliminated, leaving Portugal and Spain (four points each) and Iran (three) to compete for two spots. Spain play Morocco on Monday, while Portugal meet Iran.
If Spain and Portugal avoid defeat against Morocco and Iran they both advance. Iran will claim one of the spots if they beat Portugal or if they draw and Spain lose by more than a goal.
Portugal and Spain both have identical goal records heading into the last round so will battle it out for top spot in the group. If they both finish with exactly the same record, FIFA has set guidelines to separate teams who are on the same number of points.
Remaining fixtures on Monday:
Iran v Portugal - 20:00
Spain v Morocco - 20:00
FIFA's Soccer World Cup group ranking rules:
1. Best goal differential
2. Most goals scored
3. Points from head-to-head games between the teams involved
4. If more than two teams are tied, best goal differential from matches between the teams involved
5. Most goals scored in all matches between the teams concerned
6. Fewest points deducted based on yellow and red cards received in all group matches, as follows: a 1-point deduction for a yellow card, a 3-point deduction for a red card issued as a result of a second yellow, a 4-point deduction for a straight red, and a 5-point deduction for a straight red issued after a yellow card
7. Drawing of lots by FIFA