The Super Eagles, who defeated favourites Ivory Coast in the quarter-finals, had victory all but secured before half-time after netting three times in the first period through Elderson Echiejile, Brown Ideye and an own goal by Mohamed Sissoko.
Nigeria then added a fourth goal on the hour mark through substitute Ahmed Musa to end any hopes of a second-half fightback from Mali, whose late consolation from replacement Cheick Diarra was nowhere near enough to prevent a second successive semi-final exit.
The result sees Nigeria progress through to their seventh African Cup of Nations final and first since 2000, while Mali's bid to repeat their 1972 appearance in the title match goes on.
Nigeria do not have a great record in those finals, winning just two of six, but they will go Sunday's encounter against either Burkina Faso or Ghana with confidence soaring after building on their triumph over Ivory Coast with an impressive display at a rain-swept Moses Mabhida Stadium.
Mali, who knocked out hosts South Africa in the last eight, looked threatening early on but Nigeria gradually gained the upper hand and had already gone close a couple of times before Echiejile put them ahead in the 25th minute.
Chelsea playmaker Victor Moses did well down the right to create space and his cross into the middle found the unmarked Echiejile at the far post, and he stooped to head home from close range.
It was 2-0 five minutes later when Emmanuel Emenike's cross from the right was bundled home at the near post by Ideye, and a fantastic first period for Nigeria was completed in the 44th minute when Stephen Keshi's men added a third goal.
Ideye played a short free-kick to Emenike whose grasscutter looked set to be blocked by the wall, only for it to take a huge deflection off Sissoko and leave Mamadou Samassa in the Mali goal helpless.
Mali made two changes at the beginning of the second half in a bid to change the tide, but it was Nigeria's substitution that made the next telling contribution as Musa was sent racing clear from the halfway line before slotting through Samassa's legs to make it 4-0.
Diarra slotted home Cheick Diabate's cut-back to reduce the deficit but it was Nigeria who were left to celebrate at the full-time whistle.