The "pope's newspaper" is a paper of information and ideas at the service of truth and justice, Pope Benedict said.
L'Osservatore Romano, therefore, must continue to put focus on important issues of the day like bioethics and on women's perspectives, ecumenism and relations with Jews, the pope said.
The pope praised the Vatican paper as "one of the privileged instruments at the service of the Holy See and the Church," in a written message marking the paper's 150th anniversary.
The letter, released to journalists June 30, recognized the paper's "long and important journey" from its first issue of July 1, 1861, through today.
The paper's prestige and authority increased over time "because of its line of impartiality and courage in particular, staunchly maintained in the face of the tragedies and horrors that scarred the first half of the 20th century," the pope wrote.
The Vatican paper "was able to inform with honesty and freedom" even during the rise of totalitarianism, the horrors of the Holocaust and the persecution of Christians by communist regimes, he wrote.
Today, the paper continues to be a "guiding beacon" in a world that often lacks adequate points of reference and the presence of God, the papal letter said.
"The Holy See's daily stands as a 'paper of ideas,' an organ of formation and not only of information," it said.