Marconi married the Hon. Beatrice O'Brien, daughter of the 14th Baron Inchiquin, in London. They had three daughters: Degna (born 1908), Lucia (born 1906), and Gioia (born 1916).

Marconi and Beatrice separated in 1919 and were officially divorced in 1927. The marriage had faced difficulties due to Marconi's demanding career and travels.

Marconi married Maria Cristina Bezzi-Scali, daughter of Filippo Bezzi-Scali, a Vatican nobleman, in a civil ceremony in London. They later had a religious ceremony in Rome. They had one daughter, Elettra (born 1930).

Marconi's fourth daughter, Elettra, was born. She was named after his yacht, which he used for his experiments. The naming shows the connection he had between his family and his work.

Guglielmo Marconi died in Rome, Italy, at the age of 63, due to a heart attack. His death was mourned worldwide, recognizing his immense contribution to communication technology.