| Papal conclave February 1878 | |
|---|---|
| Dates and location | |
| 18–20 February 1878 Sistine Chapel, Apostolic Palace, Rome | |
| Key officials | |
| Dean | Luigi Amat di San Filippo e Sorso |
| Sub-dean | Camillo di Pietro |
| Camerlengo | Gioacchino Pecci |
| Protopriest | Josef Friedrich von Schwarzenberg |
| Protodeacon | Prospero Caterini |
| Election | |
| Ballots | 3 |
| Elected pope | |
| Gioacchino Pecci Name taken: Leo XIII | |
 | |
The papal conclave held from 18 to 20 February 1878 saw the election of Vincenzo Pecci, who took the name Leo XIII as pope. Held after the death of Pius IX, who had had the longest pontificate since Saint Peter, it was the first election of a pope who would not rule the Papal States. It was the first to meet in the Apostolic Palace in the Vatican because the venue used earlier in the 19th century, the Quirinal Palace, was now the palace of the king of Italy, Umberto I.