Guinea started strong, earning a 20th-minute penalty converted by Mohamed Bayo after a foul by DR Congo captain Chancel Mbemba.
But Mbemba made amends quickly, firing home an equalizer just seven minutes later.
The second half saw the momentum shift decisively towards DR Congo.
A penalty awarded for a foul on Silas was coolly converted by Yoane Wissa, putting the Leopards ahead in the 65th minute.
Guinea struggled to respond, and their fate was sealed when Arthur Masuaku’s cunning free-kick from the left flank surprised goalkeeper Ibrahim Kone, finding the net at the near post.
This victory represents a significant turnaround for DR Congo, who had drawn all four of their previous matches in the tournament.
Their penalty shootout win over Egypt in the last 16 proved a turning point, and they now find themselves in their first AFCON semi-final since 2015.
Coach Sebastien Desabre’s men will face a tough challenge in the next round, with the winner of tomorrow’s clash between Mali and hosts Ivory Coast awaiting them on Wednesday.
This promises to be another thrilling encounter as DR Congo aims to continue their remarkable journey in the Africa Cup of Nations.