Both clubs won the deciding games in their best-of-three Quarter-Final Play-Off series on Tuesday night.
In Targu Jiu, Romania, Energia rode off the partisan crowd to see off Le Mans 79-64 and extend their maiden EuroChallenge campaign.
Later in the evening in Frankfurt, Germany, hosts Fraport Skyliners came back from 21 points down to celebrate a famous 85-80 win over BC Enisey Krasnoyarsk.
Trabzonspor Medical Park and JSF Nanterre already qualified for the Final Four last Thursday, having won the first two games of their Quarter-Final Play-Off series against Avtodor Saratov and Enel Basket Brindisi respectively.
Qualifying for the Final Four marks an historical occasion for all four clubs, none of whom have previously reached the finals of a European club competition.
The venue of the 2015 EuroChallenge Final Four will be announced within the following week.
EuroChallenge Final Four Semi-Final Pairings:
Energia Targu-Jiu vs. Trabzonspor Medical Park
JSF Nanterre vs. Fraport Skyliners