Portugal and Serbia are guaranteed the top two spots. Portugal are top on goal difference after drawing 0-0 with the Republic of Ireland at the Aviva Stadium on Thursday.
The top two face each other in the final game in Lisbon on Sunday and that will decide who qualifies and who goes into the play-offs. Portugal need to avoid defeat to secure automatic qualification.
BBC SportCopyright: BBC Sport
Just as in Group A, the qualifier will be decided in tonight's final match between the top two.
Sweden started the latest round of matches top but lost 2-0 to Georgia, with Spain moving above them after a 1-0 win in Greece.
Spain lead by one point and need only a draw against Sweden in Seville, while the Swedes need to win.
Best ever campaign
Luxembourg v Republic of Ireland (19:45 GMT)
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This is Luxembourg's best ever World Cup qualification campaign, with the team winning three of their seven matches.
They beat Azerbaijan home and away along with that win over Ireland to put nine points on the board.
They had been been on a three-game losing run before Thursday's clash with Azerbaijan but managed to record a 3-1 victory in Baku.
They'll want to go out on a high tonight.
'We are an improving team'
Luxembourg v Republic of Ireland (19:45 GMT)
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Manager Stephen Kenny, whose future as Ireland manager will be decided by a review of the campaign, is confident progress has been made with only one defeat in their last nine matches, and that in heartbreaking fashion in Portugal, although a return of one win in 14 competitive fixtures remains an obvious concern.
The 50-year-old, who bristled at opposite number Luc Holtz's suggestion that his team had reverted to a long-ball approach, said: "Obviously we lost to Luxembourg in March - that last-gasp defeat in Portugal is the only match in nine since then, so we have learned a lot.
"We have a stronger squad overall with the influx of a lot of players we have brought through the system. That gives us greater competition for places, which you need.
"We are an improving team, we are improving all the time. We are not perfect, we still have some work to do to get better. We are hungry to get better, the determination, there's a great spirit in the squad.
"You have seen that recently in the last few windows. There's tremendous togetherness in the squad and we've seen a very high technical standard in recent games, against Portugal, Qatar, Azerbaijan and Serbia.
"There has been a very high technical standard overall from the players and they have shown their quality."
'Not a revenge mission'
Luxembourg v Republic of Ireland (19:45 GMT)
Republic of Ireland captain Seamus Coleman says he does not regard Sunday's World Cup qualifier away to Luxembourg as "a revenge mission".
"Revenge mission - I don't want to look at it like that in terms of I think we are in a better place," he said.
"The last few meet-ups have been good. We played some good football at times.
"We all know. I said at the time, there's no getting away from that and we have to take that on the chin, but we have to do our utmost to make sure that doesn't happen again. We are in a better place.
"We need to take that good atmosphere of how we played against Portugal into this game instead of thinking too far back and what happened."
Why Ireland aren't in the mix...
The reason the Republic of Ireland are not still in the mix for a spot in Qatar is precisely because of results like the one suffered in the reverse fixture of tonight's.
The Irish suffered a shock 1-0 defeat at the hands of Luxembourg in Dublin in March. They have managed just six points from seven games in this campaign having lost each of their first three games.
However, following their 0-0 draw against Portugal on Thursday, three points in Luxembourg would see the Republic finish third in Group A behind Portugal and Serbia, albeit only on goal difference over Sunday's opponents.
Team news - Ibrahimovic on bench
Spain v Sweden (19:45 GMT)
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It's six changes for Spain from the side that beat Greece 1-0 last time out as they prepare for their crucial match at home to Sweden.
Out go Jose Gaya, Inigo Martinez, Dani Carvajal, Rodri, Koki and Alvaro Morata.
In come Jordi Alba, Pau Torres, Cesar Azpilicueta, Carlos Soler, Sergio Busquets and Dani Olmo.
Spain starting XI: Unai Simón, Azpilicueta, Laporte, Pau Francisco Torres, Alba, Gavi, Busquets, Soler, Sarabia, Raúl de Tomás, Olmo.
For Sweden the task is simple. Win and they reach the 2022 World Cup.
They make two changes to the side that were shocked in a 2-0 loss to Georgia in their last game.
Mattias Svanberg is replaced by midfielder Albin Ekdal. Veteran striker Zlatan Imbrahimovic drops to the bench as Dejan Kulusevski comes in.
As stated in the tweet below, the Republic of Ireland make just the two changes from the team that drew against Portugal. Norwich forward Adam Idah and Wigan winger James McClean come in to the side, with Jamie McGrath and Enda Stevens dropping out.
Luxembourg have made one change from the team that beat Azerbaijan in their last game. The suspended Dirk Carlson is replaced in defence by Vahid Selimovic.
Post update
Tonight, the automatic qualification spot in Groups A and B are up for grabs, with all eyes on Portugal v Serbia and Spain's match against Sweden.
We'll be bringing you updates from those two games amongst the action from the dead rubber between Luxembourg and the Republic of Ireland.
Six World Cup qualifiers have already taken place today. There are four more to go and then we can all have a nice lie down.
Race for top spots
Getty ImagesCopyright: Getty Images
Getty ImagesCopyright: Getty Images
Denmark. Check.
Belgium. Check.
France. Check.
Germany. Check.
Croatia. Check.
Right, who's next to book their spot at Qatar 2022?
Live Reporting
Phil Dawkes, Gary Rose and Josef Rindl
All times stated are UK
Who needs what?
Portugal and Serbia are guaranteed the top two spots. Portugal are top on goal difference after drawing 0-0 with the Republic of Ireland at the Aviva Stadium on Thursday.
The top two face each other in the final game in Lisbon on Sunday and that will decide who qualifies and who goes into the play-offs. Portugal need to avoid defeat to secure automatic qualification.
Just as in Group A, the qualifier will be decided in tonight's final match between the top two.
Sweden started the latest round of matches top but lost 2-0 to Georgia, with Spain moving above them after a 1-0 win in Greece.
Spain lead by one point and need only a draw against Sweden in Seville, while the Swedes need to win.
Best ever campaign
Luxembourg v Republic of Ireland (19:45 GMT)
This is Luxembourg's best ever World Cup qualification campaign, with the team winning three of their seven matches.
They beat Azerbaijan home and away along with that win over Ireland to put nine points on the board.
They had been been on a three-game losing run before Thursday's clash with Azerbaijan but managed to record a 3-1 victory in Baku.
They'll want to go out on a high tonight.
'We are an improving team'
Luxembourg v Republic of Ireland (19:45 GMT)
Manager Stephen Kenny, whose future as Ireland manager will be decided by a review of the campaign, is confident progress has been made with only one defeat in their last nine matches, and that in heartbreaking fashion in Portugal, although a return of one win in 14 competitive fixtures remains an obvious concern.
The 50-year-old, who bristled at opposite number Luc Holtz's suggestion that his team had reverted to a long-ball approach, said: "Obviously we lost to Luxembourg in March - that last-gasp defeat in Portugal is the only match in nine since then, so we have learned a lot.
"We have a stronger squad overall with the influx of a lot of players we have brought through the system. That gives us greater competition for places, which you need.
"We are an improving team, we are improving all the time. We are not perfect, we still have some work to do to get better. We are hungry to get better, the determination, there's a great spirit in the squad.
"You have seen that recently in the last few windows. There's tremendous togetherness in the squad and we've seen a very high technical standard in recent games, against Portugal, Qatar, Azerbaijan and Serbia.
"There has been a very high technical standard overall from the players and they have shown their quality."
'Not a revenge mission'
Luxembourg v Republic of Ireland (19:45 GMT)
Republic of Ireland captain Seamus Coleman says he does not regard Sunday's World Cup qualifier away to Luxembourg as "a revenge mission".
"Revenge mission - I don't want to look at it like that in terms of I think we are in a better place," he said.
"The last few meet-ups have been good. We played some good football at times.
"We all know. I said at the time, there's no getting away from that and we have to take that on the chin, but we have to do our utmost to make sure that doesn't happen again. We are in a better place.
"We need to take that good atmosphere of how we played against Portugal into this game instead of thinking too far back and what happened."
Why Ireland aren't in the mix...
The reason the Republic of Ireland are not still in the mix for a spot in Qatar is precisely because of results like the one suffered in the reverse fixture of tonight's.
The Irish suffered a shock 1-0 defeat at the hands of Luxembourg in Dublin in March. They have managed just six points from seven games in this campaign having lost each of their first three games.
However, following their 0-0 draw against Portugal on Thursday, three points in Luxembourg would see the Republic finish third in Group A behind Portugal and Serbia, albeit only on goal difference over Sunday's opponents.
Team news - Ibrahimovic on bench
Spain v Sweden (19:45 GMT)
It's six changes for Spain from the side that beat Greece 1-0 last time out as they prepare for their crucial match at home to Sweden.
Out go Jose Gaya, Inigo Martinez, Dani Carvajal, Rodri, Koki and Alvaro Morata.
In come Jordi Alba, Pau Torres, Cesar Azpilicueta, Carlos Soler, Sergio Busquets and Dani Olmo.
Spain starting XI: Unai Simón, Azpilicueta, Laporte, Pau Francisco Torres, Alba, Gavi, Busquets, Soler, Sarabia, Raúl de Tomás, Olmo.
For Sweden the task is simple. Win and they reach the 2022 World Cup.
They make two changes to the side that were shocked in a 2-0 loss to Georgia in their last game.
Mattias Svanberg is replaced by midfielder Albin Ekdal. Veteran striker Zlatan Imbrahimovic drops to the bench as Dejan Kulusevski comes in.
Sweden starting XI: Olsen, Krafth, Nilsson, Lindelöf, Augustinsson, Kulusevski, Ekdal, Olsson, Forsberg, Isak, Claesson.
Team news
Luxembourg v Republic of Ireland (19:45 GMT)
As stated in the tweet below, the Republic of Ireland make just the two changes from the team that drew against Portugal. Norwich forward Adam Idah and Wigan winger James McClean come in to the side, with Jamie McGrath and Enda Stevens dropping out.
Luxembourg have made one change from the team that beat Azerbaijan in their last game. The suspended Dirk Carlson is replaced in defence by Vahid Selimovic.
Post update
Tonight, the automatic qualification spot in Groups A and B are up for grabs, with all eyes on Portugal v Serbia and Spain's match against Sweden.
We'll be bringing you updates from those two games amongst the action from the dead rubber between Luxembourg and the Republic of Ireland.
Six World Cup qualifiers have already taken place today. There are four more to go and then we can all have a nice lie down.
Race for top spots
Denmark. Check.
Belgium. Check.
France. Check.
Germany. Check.
Croatia. Check.
Right, who's next to book their spot at Qatar 2022?