Mali begin the tournament as one of the favourites to lift the trophy after finishing third in last year's competition.
Niger earned their place in Group B by defeating Guinea in a two-legged tie in September.
A victory for either side will give them top spot following the 2-2 draw between Ghana and DR Congo earlier on Sunday.
Read below for live updates during the match.
5.40pmHello everyone, our coverage of the Africa Cup of Nations continues tonight with this David vs. Goliath contest. Niger have never picked up a point in the competition while Mali are expected to go far this year.
5.43pmWe have some surprising team news as West Ham United's Modibo Maiga and QPR's Samba Diakite are both left out of the Mali starting lineup. Full team news is just a couple of minutes away.
5.46pmFollowing the 2-2 draw between Ghana and DR Congo earlier, a win for either side would be huge. Mali will be desperate to steal a march on their closest rivals.
5.53pmThis tournament always provides some surprises and Niger will head into this game with no fear.
5.56pmThe teams are out of the tunnel at the Nelson Madela Bay stadium and the national anthems are being played. Kick-off is just a few short moments away.
1 minThe referee blows his whistle and we're away in Port Elizabeth.
2 minMali have started the game confidently and are passing the ball around nicely.
4 minChance! Diabate has the first chance of the game as he hits the ball powerfully to test Daouda's reflexes.
6 minNiger threaten on the break but Diawara does very well to break up the attack with a sliding interception.
7 minSidibe breaks away on the right side of midfield but his cross is poor and is easily blocked. A long throw-in follows but Samassa does very well to take the catch under pressure.
9 minNiger have settled well after a nervous start and are pushing Mali back into their own half A corner comes in and this time Samassa doesn't cover himself in glory, missing the ball completely. Dankwa puts the volley wide and it's a goal kick.
12 minAnother Niger attack breaks down but Mali are struggling to keep possession. Plenty of big challenges on show early on here.
14 minMali are being restricted to long balls at the moment but Daouda is unchallenged as he collects a simple catch from Keita's cross.
16 minChance! Keita is off balance in the middle of the box and horribly miscues his shot over the crossbar. Diarra hits a volley moments later but his speculative effort is wide.
19 minMali clearly feel that set pieces will be important tonight as they send their big defenders forward for two corners. Daouda comes out to collect but he flaps at the ball. Niger clear eventually but Mali are beginning to take control.
21 minMaazou battles well to win a corner for Niger and a goalmouth scramble follows from the set piece. The loose ball drops to Dankwa but his powerful effort is superbly blocked by Samassa.
23 minBoth sides seem to be lacking a bit of composure in the final third of the pitch. Certainly not a classic so far but a goal from a corner would not be surprise.
26 minMali win a free kick in on the left side of midfield but Keita's delivery is cleared. The ball drops to the former Barcelona midfielder but his effort is blocked and rolls into the grateful hands of Daouda.
28 minMali's pressure continues as Diarra takes yet another corner. Daouda decides against coming off his line this time but Niger still manage to clear.
31 minChicoto is adjudged to have fouled S. Diarra and his namesake delivers the kick. It's a great cross but N'Diaye fails to make good contact with his effort at the back post.
33 minNiger's threat is no longer as evident as it was in the early minutes and Mali are enjoying the majority of possession, with captain Keita shining in midfield.
35 minKeita is fouled but M. Diarra wastes the free kick by smashing his shot wide from 30 yards out.
36 minTraore breaks down a Niger attack but his progress is stopped when Boubacar commits a foul.
39 minChance! Niger are beginning to look stretched in defence and they fail to close down Traore as he approaches the edge of the box. The midfielder's fires wide but that's a big let off.
40 minThere's a brief stoppage in play as Chicoto takes a knock. He's fine to continue though.
42 minKeita storms through midfield and attempts to exchange passes with Diabate. The former goes down under a challenge and appeals for a foul but the referee shakes his head.
44 minNiger are ending the half well but once again it's their failure to pick out the correct pass on the edge of the box that proves to be their downfall.
45+1 minThere's time for one more Mali set piece before half-time but Douada deals with the threat well, taking the catch shortly before the whistle is blown to bring an end to the first 45 minutes.
6.50pmHalf-time: Mali have been the better side but clear chances have been rare in a fiercely contested first half. The first goal in this game will be crucial.
6.52pmWe haven't seen as much entertainment in this one as we did in today's earlier game. Both goalkeepers look very vulnerable from set pieces so a goal from one of those situations looks likely.
6.57pmA isn't ideal for either team. Niger will need a victory if they are to spring a surprise and improve their chances of qualifying while Mali will be favourites to top the group if they can pick up three points.
7.03pmPredictably, Keita has been the standout player so far and he could make the difference this evening. Both teams are coming out of the tunnel now and we're almost ready to begin the second half.
7.05pmMali have made a change with Samassa, a striker, coming on for Cheick Diarra.
46 minThe second half is underway, can Mali find a goal or will Niger shock their opponents?
47 minDiarra breaks away on the left and his cross looks dangerous but no Mali player is able to make contact with the ball.
49 minYellow card! Soumaila is booked for a late tackle on Traore in midfield but the free kick is wasted with Keita lobbing the ball directly into the hands of Douada.
51 minSamassa has looked dangerous since his introduction and he works some space for himself on the edge of the area before dragging his shot wide of the near post.
52 minThe game is beginning to get stretched but Niger look hurried in possession and waste what could have been a dangerous counter attack.
54 minChance! Keita picks up the ball from 25 yards out before unleashing a superb strike to force Douada into a good save.
57 minNiger are wasting good opportunities too often now. The Mali defence are outnumbered on the edge of the box but Soumaila disappoints his teammates by rifling the ball into the stands.
60 minMaazou is released by a through ball but he can't control the ball well enough to evade the advancing Samassa. Good goalkeeping from the Mali man.
62 minSomeone needs to have a word with a few of these Niger players. Boubacar finds some space in midfield but instead of picking out one of his teammates, he decides to unleash a shot from 40 yards. Awful effort, shocking decision.
64 minSubstitution - Traore comes off to be replaced by former Liverpool midfielder Mohamed Sissoko.
65 minChance! Samassa looks like he's trying to prove a point. The substitute beats two defenders inside the box but he slices his effort into the side netting. Big chance missed for Mali.
68 minNiger are defending valiantly as Mali pile on the pressure. Crosses continue to be delivered but Kourouma and Bachard in particular are impressing this evening.
70 minChance! Modibo does very well to find space inside the box but his header is weak and doesn't trouble Samassa.
71 minTamboura is a dangerous player for Mali and he delivers an inviting cross towards Diabate but Douda reacts quickly and collects the ball at the second time of asking.
73 minChance! Big opportunity for Niger to take the lead! Boubacar's corner is beautifully directed but Maazou can't direct his header on target despite a giant leap.
75 minYellow card! Boubacar is shown the yellow card for a clear foul on M. Traore.
76 minChance! Maazou picks up the ball just inside the Mali half before beating three players. He chooses to shoot from the edge of the area but his effort is wide and he maybe could have picked out a teammate.
78 minChance! A brilliant move from Mali ends with the ball at the feet of Keita on the edge of the box but the skipper is left frustrated when his strike crashes against the crossbar.
79 minSubstitutions - Boubacar comes off to be replaced by Talatou Djibo for Niger while QPR's Diakite comes on for Diarra as Mali go in search of a winner.
80 minChance! Tamboura once again creates space for himself on the wing but his perfect delivery is headed over by Traore. Mali may live to regret these misses.
81 minChance! Maazou whips in an inviting cross and Soumalia gets a toe on the ball but Samassa holds on in the Mali goal.
83 minMali are beginning to take more of a direct approach in the closing stages but the long balls are just not finding their targets at the moment.
84 minDiabate battles to win possession in the box but his effort is blocked and Niger recover to clear the danger.
85 minI mentioned Daouda's vulnerability earlier and he'll be unhappy with himself here. A high cross comes in but the goalkeeper fails to collect and Keita reacts quickest to finish smartly. The skipper may have just won the match for his side there and he deserves his goal tonight.
87 minNiger are trying their hardest to find a way back into this match but Mali are holding firm in defence. Three minutes of normal time remaining in Port Elizabeth.
89 minThe trailing team win a corner but Mali look organised in defence and the ball is cleared. Long balls just don't seem to be working for Niger and they are lacking a creative influence in midfield.
90 minThe fourth official reveals that there will be four minutes of added time.
90+1 minMali are looking relaxed now and continue to pass the ball around nicely. Niger are struggling to get out of their half now.
90+4 minNiger deliver a deep cross from a free kick but Samassa is brave and takes a very good catch. That should be just about it for tonight.
7.55pmFull-time: The final whistle goes and Mali have started their campaign with a crucial victory. Niger battled well but Keita's late goal is enough to earn his side three points.
7.57pmMali go top of the group on three points while Ghana and DR Congo both have one. Niger will have to produce something special if they are to stand any chance of qualifying following yet another Africa Cup of Nations match where they have failed to pick up a point.
7.58pmThat's the end of our coverage tonight and I'd like to thank you for joining me. Make sure you stick with Sports Mole as we continue to bring you the best of this fascinating competition.