If they win, they will become the nation with the smallest population ever to qualify for the finals.
Courageous and fearsome in their approach and appearance, Iceland wiped the football world off of their feet with a 2-1 victory over England which send them straight into the quarterfinals.
Icelandic football team has not enjoyed notable success until the 21st century and it was exactly in the previous World Cup qualifiers - for the 2014 edition in Brazil - that the football world first took notice of Vikings.
Several giants of the world game are struggling for qualification for the World Cup with three-time runners up the Netherlands all but out, while Portugal and Switzerland face a huge match to see who finishes top of European qualifying Group B on Tuesday night.
Hallgrimsson knows that it is the World Cup that forged the legends of the game's all-time greats, and that his players - many of whom were unknowns prior to EURO 2016 - will now have a chance to make their mark. Iceland beat Kosovo 2-0 and Liverpool's Mohamed Salah took Eygpt to an emphatic 2-1 win over Congo.
It was only two years ago that Iceland qualified for a major finals for the first time, taking advantage of a tournament expanded to 24 teams but nonetheless knocking out the Netherlands in qualifying. "It is much harder for the World Cup".
In other results, Austria won 1-0 in Moldova in Group D, Finland and Turkey finished 2-2 in Group I, and Macedonia beat Liechtenstein 4-0 in Group G.
And while we're sure Iceland's celebrations are still well and truly underway - anyone heading to Russian Federation next year now has around eight months to prepare for scenes like this.
Italy - already certain of a play-off place behind Spain - ended their campaign with a 1-0 over Albania in Shkoder, Antonio Candreva scoring in the 73rd minute.