San Francisco are one game away from the Super Bowl after edging out New Orleans 36-32 in one of the finest playoff games in NFL history.
The lead changed hands four times in as many minutes at the end of an enthralling encounter, with the 49ers sealing victory with just nine seconds remaining.
Alex Smith masterminded the winning drive before Vernon Davis somehow survived a brutal hit to cling onto the quarterback's 14-yard touchdown pass for the decisive score.
The 49ers - who dominated the sport for much of the late 1980s and early 90s with future Hall of Famers Joe Montana, Steve Young and Jerry Rice - will meet the New York Giants who beat the Green Bay Packers 37-20
San Francisco's success under rookie head coach Jim Harbaugh was not widely predicted but his pragmatic and unspectacular approach could yet prove the old adage that while "offences win games, defences win championships".
Many thought that old cliche was dead in the modern era, which is dominated by high-scoring offences largely reliant on the passing game.
None more so than the Saints, whose quarterback Drew Brees recently smashed Dan Marino's 27-year-old record for the most passing yards in a regular season.
But it was to be another old saying that would really do for the Saints - that turnovers often prove fatal.
The 49ers twice intercepted Brees and forced three fumbles. To put the 49ers' defence and special teams' heroics into perspective, the Saints had only previously suffered five fumbles all season.
Even so, Saints fans will consider themselves unlucky after bravely battling back from a nightmare start which saw them trail 17-0 at the start of the second quarter following Smith's touchdown passes of 49 yards and four yards respectively to Davis and Michael Crabtree.
Brees responded with a pair of touchdown passes of his own, to Jimmy Graham (14 yards) and Marques Colston (25).
Defences then took over, restricting both teams to field goals to leave the 49ers 20-14 ahead with little more than four minutes remaining in the fourth quarter.
Then the fireworks really began.
The diminutive but eel-like Darren Sproles caught a 44-yard pass from Brees to level things up before the point-after gave the visiting Saints the lead for the first time.
Not to be outdone, Smith restored the Niners' lead with a cleverly designed and perfectly executed 28-yard touchdown run down the left sideline.
But still the Saints were not done. Graham caught another long pass from Brees, evaded the 49ers' lunging secondary and completed a 66-yard touchdown to silence the majority in the Candlestick Park crowd.
A successful two-point conversion then meant the Saints, with only 1.37 remaining, led 32-29.
And so began the drive which will cement Smith - who has until now largely struggled to cope with the pressure of being the number one pick in the 2005 draft - a place in 49ers history alongside Montana and Young.
Down to one timeout and starting from his own 15 yard line, he marched his team down the field in one last, do-or-die, effort.
Having successfully got into David Akers' field goal range, most assumed the 49ers would play conservatively, kick the three points, and take the game into overtime.
But Smith seized the day and his accurate bullet pass found Davis to the delight of the Red and Gold army and set up a meeting with either the Packers or Giants next Sunday.
The first AFC divisional playoff, however, was far less dramatic as the New England Patriots blitzed the Denver Broncos 45-10.
In a game billed as the battle of the quarterbacks - the classical style of consistently brilliant Tom Brady against the young upstart Tim Tebow - the old master firmly put on a masterclass for the rookie.
Brady, who tied a playoff record with six touchdown passes, including three to one of the standout players of the season tight end Rob Gronkowski, was practically perfect.
Meanwhile Tebow, famed for his devout faith and "Tebowing" celebrations in which he kneels down to pray, simply could not compete.
He completed only nine passes from 26 attempts, for just 136 yards, and will know that he needs to do a lot more in future seasons to win over critics yet to be convinced of credentials to be an elite quarterback.
With homefield advantage guaranteed throughout the playoffs, courtesy of their outstanding regular season record, the Patriots will next Sunday welcome to Foxborough the Baltimore Ravens.