It is the first time United have reached the Champions League final since winning the trophy against Barcelona in 1999, the year of their famous 'Treble'. And it was particularly sweet for Scholes who missed that match through the suspension.
This semi-final was frantic at times with both teams wanting to attack but United took the lead in spectacular fashion early on.
Ronaldo's run was blocked by the Barca defence but Carles Puyol's clearance fell perfectly for Scholes to rifle a rising shot high into the roof of the net from fully 30 yards.
The goal raised the noise levels at Old Trafford and United had good opportunities to add to their lead.
Ji-Sung Park, for instance, slid a first-time effort from Ronaldo cut-back only inches wide. And then the Korean star sent over a perfect cross for Nani - only to see his team-mate send his header wastefully past the post.
Barcelona created opportunities to score, too. Deco struck two well-hit shots narrowly wide of the target and the lively Leo Messi saw an effort well saved by Edwin van der Sar following a typically exciting run down the right flank.
But half-time arrived with United still narrowly ahead and Old Trafford knew it was in for a nervy finale.
The home side were playing without Wayne Rooney, who injured his hip in last weekend's Premier League defeat at Chelsea. So manager Sir Alex Ferguson chose to field winger Ronaldo up front alongside Carlos Tevez with Park and Nani on the flanks.
United needed a good performance after the drama of Stamford Bridge, where they not only lost 2-1 but were also involved in a melee with Chelsea groundstaff after the match.
That incident is being investigated by The FA but it was quickly forgotten tonight as Scholes grabbed his glory goal.
Barcelona brought on both Thierry Henry and wonder kid Bojan in a bid to grab an equaliser but with United's defence, and in particular Rio Ferdinand, outstanding they were expertly kept at bay.
Korean star Park was also impressive while Ronaldo, although unable to produce his customary magic, worked unselfishly for his team in a central striker's role.
Goalscorer Scholes and winger Nani were replaced by Darren Fletcher and Ryan Giggs with 13 minutes to go before Henry wasted a good headed chance by sending his effort straight at van der Sar.
There were a nervy few minutes at the end and a late injury to defender Patrice Evra. But United held on for a famous victory and will now wait to see if Chelsea or Liverpool await them in the final.