|Archpriest of the Basilica di Santa Maria Maggiore|
|Church||Roman Catholic Church|
|Appointed||15 December 1986|
|Term ended||22 August 1990|
|Other post(s)||Cardinal-Deacon of San Pio V a Villa Carpegna (1985-90)|
|Ordination||22 May 1937|
|Consecration||8 December 1961|
by Amleto Giovanni Cicognani
|Created cardinal||25 May 1985|
by Pope John Paul II
28 September 1914
|Died||22 August 1990 (aged 75)|
Policlinico Agostino Gemelli, Rome, Italy
|Motto||Sola virtus manet|
|Coat of arms|
|Reference style||His Eminence|
|Spoken style||Your Eminence|
|See||Lerus (titular see|
Luigi Dadaglio (28 September 1914 - 22 August 1990) was a Roman Catholic Cardinal and Major Penitentiary of the Apostolic Penitentiary.
He was born in Sezzadio, Italy. He was educated at the Seminary of Acqui. He was ordained on 22 May 1937. From 1938 until 1942 he continued his studies at the Pontifical Lateran University where he earned a doctorate in utroque iure (in both canon and civil law). He later studied at the Pontifical Ecclesiastical Academy in Rome where from 1941 until 1943 he studied diplomacy.
He joined the Vatican Secretariat of State (section of Ordinary Affairs) in 1942. He was the secretary in the nunciature in Haiti and Dominican Republic from 1946 until 1950 when he was promoted to be the Auditor in the apostolic delegation to the United States, until 1953. He served as auditor in Canada and in Australia also. He was transferred to be the counselor in the nunciature in Colombia from 1958 until 1960. He was in charge, provisionally, of the nunciature in Venezuela in April 1960, until he himself was named Nuncio in Venezuela on 28 October 1961.
He was appointed titular Archbishop of Lerus by Pope John XXIII. He was consecrated on 8 December 1961 by Amleto Giovanni Cicognani, Cardinal Secretary of State, who was assisted by Archbishop Angelo Dell'Acqua, substitute of the Secretariat of State. He attended the Second Vatican Council. He was appointed Apostolic Nuncio to Spain on 8 July 1967. He was named Secretary of the Congregation for Divine Worship and the Discipline of the Sacraments on 4 October 1980. Pope John Paul II named him Pro-Major Penitentiary on 8 April 1984.
He was created and proclaimed Cardinal-Deacon of S. Pio V a Villa Carpegna in the consistory of 25 May 1985. Having been created a Cardinal he was then named full Major Penitentiary two days later. He was named Archpriest of the Basilica di Santa Maria Maggiore in 1986. He resigned the penitentiary on 6 April 1990. He died on 22 August.