Galatasaray’s Turkish forward Kerem Akturkoglu scored a hat-trick, including the opener in the first half.
Argentine star Mauro Icardi scored on a penalty kick in the first 45 minutes.
Basaksehir defender Youssouf Ndayishimiye scored an own goal as the visitors went into the break 3-0.
Confident play from Galatasaray hinted at a big win.
Akturkoglu found the net twice in the second half. Belgian forward Dries Mertens scored and Turkish defender Abdulkerim Bardakci scored a late header to seal the victory for Galatasaray.
It was a huge disappointment for Basaksehir, the 2020 Turkish champions.
Following the large win, Galatasaray crept closer to league leaders and archrivals, Fenerbahce.
Second-place Galatasaray have 27 points in 13 matches and are two points behind Fenerbahce.
Fenerbahce were handed an unexpected2-1 loss to Bitexen Giresunspor at home in Ulker Stadium earlier Saturday.
The Super Lig will enter a break after Sunday’s matches as the 2022 FIFA World Cup will begin Nov. 20 in Qatar.
Source: Anadolu Agency