The highlights are above for you to enjoy, while you can scroll back through for more clips and analysis and reaction from both sides and the Test Match Special team.
We'll be back at 09:15 BST on Tuesday for South Africa against Bangladesh.
See you then.
Post update
We expect sides to need at least 10 points, maybe 12 to reach the final four.
Both of these sides are on four points from five games now.
Pakistan have games against South Africa (27 Oct), Bangladesh (31 Oct), New Zealand (4 Nov) and England (11 Nov) remaining.
Afghanistan face Sri Lanka (30 Oct) before matches against the Netherlands (3 Nov), Australia (7 Nov) and South Africa (10 Nov).
Both have tough games remaining but do Afghanistan have a more favourable run? Quite possibly.
Post update
Also, how crucial was this wicket of Iftikhar Ahmed off the second ball of the final over?
He'd smashed 40 off 27 balls, including four sixes, and another four balls of him could have added another 10 runs on Afghanistan's chase.
That would have made it tricky.
Post update
A lot of attention will be on Afghanistan's batting line-up after that chase, but a special mention for 18-year-old spinner Noor Ahmad.
The left-armer took 3-49 on his World Cup debut. They were key wickets too, the set Abdullah Shafique and Babar Azam and the dangerous Muhammad Rizwan.
Pakistan struggled to play him and he could be a key part of Afghanistan's side for the remainder of this competition.
'I don't know where Pakistan go from here'
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
You thought it was a little bit of dew but the way it was bouncing inconsistently, it did not look like a big dew factor. You felt as though every time Pakistan were coming back into the game, there was bad delivery after bad delivery, mixed in with some good running from Afghanistan.
If you were going to get purchase off any pitch in India, it was Chennai. Why were you protecting your spinners? Get 30 overs from your spinners. Pakistan's bowling was atrocious and moving forward, I don't really know where they go from here. I well and truly don't.
'Historic World Cup for our country and people'
Afghanistan captain Hashmatullah Shahidi: "Yes, this win tastes nice!
"The way we chased was very professional and the way we did that will help us going into our other games now.
"We are playing quality cricket. We have always had belief and at the start of the tournament I told my team I wanted to make it a historic one for our country and our people. We did that against England and now today against Pakistan.
"We are looking forward to playing positive cricket in our next games.
"Our bowling was very good, especially our spinners. We gave Noor a chance and trusted his talent. But with the bat, the way we started the innings gave us a lot of confidence and momentum.
"We had the game in our hands from the beginning until the end and the partnership between myself and Rahmat was also very good."
"We got a good total. Our bowling is not up to the mark.
"In World Cups you need all three departments firing and we haven't done that. Afghanistan played very well but we gave them a lot of runs and it cost us.
"We stuck to our plan in the middle overs but we needed wickets and we couldn't get them.
"We were backing ourselves to win today. But they played well in all three departments and we didn't. We have got to put that right in our next match.
"We didn't hit the right lengths, especially with our spinners. We would bowl a few dot balls and build pressure but then a bad ball would give them a boundary."
Post update
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
None of Pakistan's batters are getting above 60/70/80 and getting that big score that wins you matches. We thought what they got at half-time was enough, but you don't want to see a card that doesn't have a really big score on it. It does not look like a 300 wicket but that is symptomatic of how they have batted in this World Cup.
Post update
Simon Mann
BBC Test Match Special commentator
A devastating defeat for Pakistan, they have now won two and last three. They have only beaten Sri Lanka and the Netherlands. Their World Cup hopes hang by a thread and they are really against it.
'Tonight is about Afghanistan, not Pakistan'
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
You have to praise Afghanistan and how much their batting order has been able to build an innings. All of their top four can bat. Ibrahim Zadran is excellent, he has an arrogance but it is not a naughty arrogance. With the new ball, his ability to get on top of it and hit into the square. He and Gurbaz set a platform.
Rahmat Shat and the captain Hashmatullham were able to carry that on, it only really slowed down just before the game was almost won. I just love how they had composure and control. They ran loads of twos and the skill to get through the ball, the intensity and commitment and they sped for second runs and capitalised on overthrows.
Every time Pakistan made an error, they pounced on it. They deserved their victory and tonight is about Afghanistan more than it is Pakistan.
Post update
Even when Rahmanullah Gurbaz and Ibrahim Zadran were dismissed, Afghanistan didn't panic.
At 190-2 they were well set, but needing 93 more for just a third World Cup win and your first success against Pakistan there were bound to be nerves.
Rahmat Shah and Hashmatullah Shahidi didn't show it though. They even soaked up the pressure sustained by 11 consecutive dot balls and won with six balls to spare.
Post update
Simon Mann
BBC Test Match Special commentator
The only thing Ibrahim Zadran has missed today is the lap of honour because of doing interviews.
Post update
Player of the match Ibrahim Zadran: "I wanted to go out with positive intent and with a positive mind.
"Me and Gurbaz have put on a lot of good partnerships together. We have played together since we were 16 so we always have good communication.
"The support from him at the other end was very important and gave the team good momentum.
"In this kind of event, this is so big for me. I am feeling very proud of myself and for my country."
Post update
Where do you start with that chase? It was perfectly judged and time, almost in a classic Jonathan Trott manner. There was never any fuss or panic.
It was built on a superb platform of 130 laid by Rahmanullah Gurbaz and Ibrahim Zadran.
It was their second century stand of the tournament. They are the only opening pair to do that.
Post update
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
That is how you want to chase a game. A complete batting performance. The top four got 286 by themselves. Afghanistan never looked in trouble, you never thought they were going to lose. We all thought there may be a collapse but it wasn't even close. At what point do we say these wins are no longer upsets?
Post update
Here's how the World Cup table looks after that win for Afghanistan.
It leaves England bottom of the pile, but actually with games against Pakistan and Australia to come it is probably the result they wanted.
BBC SportCopyright: BBC Sport
Post update
Afghanistan are currently doing a lap of honour around the MA Chidambaram Stadium in Chennai.
Rashid Khan has just screamed into the camera in excitement.
He's a global superstar and plays in every franchise league going but it is these moments he'll remember when he retires.
Post update
Geoff Lemon
BBC Test Match Special commentator
Afghanistan's team are out on the pitch together. Rashid Khan has the Afghanistan flag around his neck like scarf. Mohammad Nabi has been with this team right since the beginning and now, they have a second win in this World Cup. Spare a thought for Pakistan, they are in strife right now.
Post update
Captain Hashmatullah Shahidi flicked away the winning runs and finishes unbeaten on 48.
Live Reporting
Callum Matthews, Ffion Wynne and Tom Mallows
All times stated are UK
BBC SportCopyright: BBC Sport 
Latest PostPost update
Time for us to leave it there for today.
Here's Tom Mallows' report as Afghanistan stun Pakistan for just their third World Cup win.
The highlights are above for you to enjoy, while you can scroll back through for more clips and analysis and reaction from both sides and the Test Match Special team.
England's Joe Root has also been speaking today and he's suggested they don't play enough 50-over cricket.
We'll be back at 09:15 BST on Tuesday for South Africa against Bangladesh.
See you then.
Post update
We expect sides to need at least 10 points, maybe 12 to reach the final four.
Both of these sides are on four points from five games now.
Pakistan have games against South Africa (27 Oct), Bangladesh (31 Oct), New Zealand (4 Nov) and England (11 Nov) remaining.
Afghanistan face Sri Lanka (30 Oct) before matches against the Netherlands (3 Nov), Australia (7 Nov) and South Africa (10 Nov).
Both have tough games remaining but do Afghanistan have a more favourable run? Quite possibly.
Post update
Also, how crucial was this wicket of Iftikhar Ahmed off the second ball of the final over?
He'd smashed 40 off 27 balls, including four sixes, and another four balls of him could have added another 10 runs on Afghanistan's chase.
That would have made it tricky.
Post update
A lot of attention will be on Afghanistan's batting line-up after that chase, but a special mention for 18-year-old spinner Noor Ahmad.
The left-armer took 3-49 on his World Cup debut. They were key wickets too, the set Abdullah Shafique and Babar Azam and the dangerous Muhammad Rizwan.
Pakistan struggled to play him and he could be a key part of Afghanistan's side for the remainder of this competition.
'I don't know where Pakistan go from here'
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
You thought it was a little bit of dew but the way it was bouncing inconsistently, it did not look like a big dew factor. You felt as though every time Pakistan were coming back into the game, there was bad delivery after bad delivery, mixed in with some good running from Afghanistan.
If you were going to get purchase off any pitch in India, it was Chennai. Why were you protecting your spinners? Get 30 overs from your spinners. Pakistan's bowling was atrocious and moving forward, I don't really know where they go from here. I well and truly don't.
'Historic World Cup for our country and people'
Afghanistan captain Hashmatullah Shahidi: "Yes, this win tastes nice!
"The way we chased was very professional and the way we did that will help us going into our other games now.
"We are playing quality cricket. We have always had belief and at the start of the tournament I told my team I wanted to make it a historic one for our country and our people. We did that against England and now today against Pakistan.
"We are looking forward to playing positive cricket in our next games.
"Our bowling was very good, especially our spinners. We gave Noor a chance and trusted his talent. But with the bat, the way we started the innings gave us a lot of confidence and momentum.
"We had the game in our hands from the beginning until the end and the partnership between myself and Rahmat was also very good."
Post update
Here's the winning moment.
Come for the moment and stay for the scenes.
'Our bowling is not up to the mark'
Pakistan captain Babar Azam: "That really hurt us.
"We got a good total. Our bowling is not up to the mark.
"In World Cups you need all three departments firing and we haven't done that. Afghanistan played very well but we gave them a lot of runs and it cost us.
"We stuck to our plan in the middle overs but we needed wickets and we couldn't get them.
"We were backing ourselves to win today. But they played well in all three departments and we didn't. We have got to put that right in our next match.
"We didn't hit the right lengths, especially with our spinners. We would bowl a few dot balls and build pressure but then a bad ball would give them a boundary."
Post update
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
None of Pakistan's batters are getting above 60/70/80 and getting that big score that wins you matches. We thought what they got at half-time was enough, but you don't want to see a card that doesn't have a really big score on it. It does not look like a 300 wicket but that is symptomatic of how they have batted in this World Cup.
Post update
Simon Mann
BBC Test Match Special commentator
A devastating defeat for Pakistan, they have now won two and last three. They have only beaten Sri Lanka and the Netherlands. Their World Cup hopes hang by a thread and they are really against it.
'Tonight is about Afghanistan, not Pakistan'
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
You have to praise Afghanistan and how much their batting order has been able to build an innings. All of their top four can bat. Ibrahim Zadran is excellent, he has an arrogance but it is not a naughty arrogance. With the new ball, his ability to get on top of it and hit into the square. He and Gurbaz set a platform.
Rahmat Shat and the captain Hashmatullham were able to carry that on, it only really slowed down just before the game was almost won. I just love how they had composure and control. They ran loads of twos and the skill to get through the ball, the intensity and commitment and they sped for second runs and capitalised on overthrows.
Every time Pakistan made an error, they pounced on it. They deserved their victory and tonight is about Afghanistan more than it is Pakistan.
Post update
Even when Rahmanullah Gurbaz and Ibrahim Zadran were dismissed, Afghanistan didn't panic.
At 190-2 they were well set, but needing 93 more for just a third World Cup win and your first success against Pakistan there were bound to be nerves.
Rahmat Shah and Hashmatullah Shahidi didn't show it though. They even soaked up the pressure sustained by 11 consecutive dot balls and won with six balls to spare.
Post update
Simon Mann
BBC Test Match Special commentator
The only thing Ibrahim Zadran has missed today is the lap of honour because of doing interviews.
Post update
Player of the match Ibrahim Zadran: "I wanted to go out with positive intent and with a positive mind.
"Me and Gurbaz have put on a lot of good partnerships together. We have played together since we were 16 so we always have good communication.
"The support from him at the other end was very important and gave the team good momentum.
"In this kind of event, this is so big for me. I am feeling very proud of myself and for my country."
Post update
Where do you start with that chase? It was perfectly judged and time, almost in a classic Jonathan Trott manner. There was never any fuss or panic.
It was built on a superb platform of 130 laid by Rahmanullah Gurbaz and Ibrahim Zadran.
It was their second century stand of the tournament. They are the only opening pair to do that.
Post update
Carlos Brathwaite
Ex-West Indies all-rounder on BBC Test Match Special
That is how you want to chase a game. A complete batting performance. The top four got 286 by themselves. Afghanistan never looked in trouble, you never thought they were going to lose. We all thought there may be a collapse but it wasn't even close. At what point do we say these wins are no longer upsets?
Post update
Here's how the World Cup table looks after that win for Afghanistan.
It leaves England bottom of the pile, but actually with games against Pakistan and Australia to come it is probably the result they wanted.
Post update
Afghanistan are currently doing a lap of honour around the MA Chidambaram Stadium in Chennai.
Rashid Khan has just screamed into the camera in excitement.
He's a global superstar and plays in every franchise league going but it is these moments he'll remember when he retires.
Post update
Geoff Lemon
BBC Test Match Special commentator
Afghanistan's team are out on the pitch together. Rashid Khan has the Afghanistan flag around his neck like scarf. Mohammad Nabi has been with this team right since the beginning and now, they have a second win in this World Cup. Spare a thought for Pakistan, they are in strife right now.
Post update
Captain Hashmatullah Shahidi flicked away the winning runs and finishes unbeaten on 48.
Rahmat Shah is 77 not out at the other end.
The pair shared an unbroken 96 from 93 balls.