Lithuanian President Gitanas Nauseda appointed him last week for a term of five years upon approval of the Seimas. He is replacing Lieutenant General Jonas Vytautas Zukas who might become the president's advisor.
Rupsys, 52, has in the past commanded various military units and has held the post of director of the Personnel Department at the Defense Ministry.
He was appointed the commander of the Lithuanian Land Force in 2016 and received the rank of brigadier general two years later.
Rupsys graduated from the General Jonas Zemaitis Military Academy of Lithuania, the Estonia-based Baltic Defense College, and the US Army War College.
Also on Wednesday, the changeover of the country's Land Force command will take place and Brigadier General Raimundas Vaiksnoras will take over as commander of the Land Force.
And Brigadier General Gintautas Zenkevicius will become the chief of Defense Staff in late July.