Chris Martin Plunges Through Trapdoor at Australian Concert

Chris Martin fell through his stage at the “Speed of Sound” … stepping backward while performing with Coldplay in Australia — and falling straight through a trapdoor onstage.

The singer-songwriter hopped onstage with the band for the fourth and final Melbourne date on their “Music of the Spheres” tour … and, he should’ve kept his eyes on the ground ’cause he stepped in the wrong spot and almost took a nasty tumble.

Watch the video … Martin’s reading out signs he sees in the crowd in between songs when he steps backward and falls — thankfully, into the waiting arms of a crewmember — who stops him from smacking into the harsh floor.