Matt Ebden will be the lowest-ranked semifinalist in tournament history after an upset of former champion Karen Khachanov in the Open 13 Provence.
Ranked world No.287, Ebden stunned the world No.21 Russian with a 4-6 6-4 6-2 win.
A qualifier at the ATP 250 tournament, the Australian has now won five straight matches in Marseille.
It ensures a further push towards the world top 200 for Ebden, who started the 2021 season at world No.314.
The 33-year-old Ebden utilised all his experience against the No.3 seed Khachanov, recovering from a first-set deficit with a decisive break of serve in the fifth game of the second set.
He raced to a 5-1 lead with a double break of the Khachanov serve in the third set, eventually closing out victory in one hour, 49 minutes.
Ebden has now established a 6-2 match-winning record for the 2021 season, after earlier progressing to the Singapore quarterfinals. He did not contest any tour-level matches last year.
The former top-40 Australian - who stressed his determination for a big season during the Australian summer - has a chance to build on his impressive momentum when he faces Daniil Medvedev in the semifinals.
Adding to a stunning week in the French city, Ebden has also progressed to the doubles semifinal with countryman Matt Reid.
The Australian duo yesterday defeated Spaniards Alejandro Davidovich Fokina and Marc Lopez 7-6(5) 6-1. They'll face Lloyd Grasspool and Harri Heliovaara next.
Results:
Men's singles, quarterfinal
[Q] Matthew Ebden (AUS) d [3] Karen Khachanov [RUS] 4-6 6-4 6-2
Men's singles, quarterfinal
Matthew Ebden (AUS)/Matt Reid (AUS) d Alejandro Davidovich Fokina (ESP)/Marc Lopez (ESP) 7-6(5) 6-1
Coming up:
Men's singles, semifinal
[Q] Matthew Ebden (AUS) v [1] Daniil Medevedev [RUS]
Men's doubles, semifinal
Matthew Ebden (AUS)/Matt Reid (AUS) v Lloyd Grasspool (GBR) and Harri Heliovaara (FIN)