This game represented a huge opportunity for Sunderland to boost their hopes of European qualification, and they had the first chance when Chris Rigg ghosted in from the right flank, but the 18-year-old’s effort was tame and Matz Sels gathered easily.
That was as good as it got for the hosts in a nightmare first half, and they went behind after 17 minutes when Igor Jesus’ far-post header cannoned off Trai Hume into the net for an own-goal.
The Black Cats’ luck was out for the opening goal, but they were entirely responsible for their own downfall in the 31st minute as Forest made it 2-0.
Goalkeeper Robin Roefs passed straight to Chris Wood, who received the ball back from Morgan Gibbs-White and slotted home his first PL goal since the opening day of the season.
It got worse for Sunderland three minutes later, when Jesus had time to nod a cross towards the penalty spot and Gibbs-White fired in his sixth goal in six games across all competitions.
The home fans were already streaming out when Forest made it 4-0 eight minutes before half time, as Ola Aina’s effort deflected kindly for Jesus to hammer a first-time volley past Roefs for his second goal in as many matches.
Sunderland started the second half with a point to prove, and Dan Ballard thought he had pulled a goal back when he headed home from close range in the 61st minute, but referee Darren England ruled it out for an apparent foul by Nordi Mukiele on Sels after consulting the VAR monitor.
That decision extinguished any faint hopes of a comeback for the Black Cats, as they began to face up to a fourth defeat in five games at the Stadium of Light (W1) - having gone unbeaten in their first 12 home matches of the PL campaign.
Forest accumulated more bookings (five) than shots (one) after the interval, but they made that single effort count as Newcastle United academy graduate Elliot Anderson rubbed salt in Sunderland’s wounds by sweeping home the fifth goal in stoppage time.
That came after Sels had tipped Enzo Le Fée’s late piledriver over the crossbar to preserve his clean sheet as Vítor Pereira’s men took a giant step towards safety, while stretching their unbeaten run to eight games across all competitions (W5, D3).
Forest can now look forward to Thursday’s UEFA Europa League semi-final first leg against Aston Villa after scoring four goals in each of the past two matches, while Sunderland have conceded exactly that number and remain 11th in the table.