Check out the new pics from the scene -- mega-fans have already begun congregating on Olympic Way outside the famed London stadium ... where Taylor is set to perform 5 sold-out nights, her final stop on the European leg of her Eras Tour.

Swifties aren't the only ones showing up in droves -- there is an increased amount of security lined up outside the venue, as well. Though, we're sure some fans are about to be turned away ... as TMZ previously reported, Tay-gating has been outright banned during TS's latest London stop.

For those who haven't been following the Eras Tour closely -- Swifties who weren't able to secure tickets to the sold-out run have been camping outside various venues to take in whatever they can from Taylor's 3.5-hour-long sets.

In fact, 40,000 people packed themselves onto a hillside in Munich just so they could hear "Shake It Off" from a distance.

However, following the arrests of 3 male teens in Vienna, who allegedly planned a terrorist attack on Taylor's since-canceled Austrian shows, exterior crowds have been prohibited, at least at Wembley Stadium.

Sources previously told us that Taylor's Wembley security detail isn't taking any risks  ... as extra private counterterrorism experts have been tapped to beef up the protection.