Waldemar Stanisław Sommertag (born 6 February 1968) is a Polish prelate of the Catholic Church who works in the diplomatic service of the Holy See.

[1] On 15 February 2018, Pope Francis appointed him titular archbishop of Traiectum ad Mosam and Apostolic Nuncio to Nicaragua.

For three years he quietly assisted in negotiations between the government and the families of its imprisoned critics, winning release for some, but he then began to use the term "political prisoners".

On 18 November 2021, the Nicaraguan government decreed the abolition of the title "dean of the diplomatic corps", traditional accorded in Catholic countries to the representative of the Holy See.

[5][a] On 6 March 2022, he left Nicaragua after the government withdrew its acceptance of his diplomatic status, requiring him to leave the country.