The German presented Lithuanian President Gitanas Nauseda with his credentials as Apostolic Nuncio for Estonia, Latvia and Lithuania on Friday, according to the head of state's website.
Nauseda congratulated Gänswein on his arrival in Lithuania and on his 40th anniversary as a priest, which he celebrated in May.
As secretary to Joseph Ratzinger/BenedictXVI (1927-2022), Gänswein was one of the most prominent Germans in the Vatican for many years.
Photos from the Office of the President show Gänswein in a black cassock with the purple sash of an archbishop and a cape of the same colour as he walks down the red carpet into the presidential palace.
There, the credentials were handed over in front of the flags of Lithuania and the Vatican.
Help for Ukraine
Catholic Lithuania has always had a special relationship with the Holy See and will not forget that the latter never recognised the occupation and annexation of the Baltic country by the Soviet Union, said the President.
Lithuania's Church had been an important pillar of the country's internal strength during both the Soviet and Tsarist Russian occupations.
After independence, the visit of Pope John Paul II and his words "Fear not!" gave Lithuania courage. These three words are as relevant today as ever in view of Russia's attack on Ukraine, said the head of state.
Nauseda called on the international community to help Ukraine in its defence. He appealed to the Vatican to maintain its strong support for Ukraine, which he greatly appreciated, as well as the Catholic Church's help for Ukrainian refugees.
Any scenario other than a victory for Ukraine would have negative consequences for Europe and its security, the President emphasised.
Future peace must be based on full support for Ukraine's independence, sovereignty and territorial integrity, the head of state said.
Pope Francis had transferred Gänswein to his home diocese of Freiburg in 2023 without assigning him an office.
In June 2024, Francis appointed Benedict XVI's long-time private secretary as Vatican ambassador to Lithuania, Latvia and Estonia.