Lacher has held the position on an interim basis since October 2016, succeeding Alexandre Zeller, who stepped down in September.
Based in Switzerland, Lacher holds various roles at Credit Suisse, which he will be giving up at the end of February.
Lacher welcomed the opportunity to become the permanent chair of the board at SIX as it deals with current and upcoming challenges.
He said: "SIX is well positioned, but is confronted by some major challenges. It operates in an extremely demanding environment. Our clients' business models continue to be under pressure. This is on account of various factors ranging from the current low interest rates and new regulatory provisions to technological changes. The pace of change has very much accelerated, which is having an impact on the business model and operations of SIX.”
“I am nevertheless confident that these developments also offer new earnings opportunities to SIX. It is now up to the board of directors, group executive board and employees of SIX to seize them together."