Broglie Obelisk, Neoclassical obelisk in Monrepos Park, Vyborg, Russia.

The Broglie Obelisk is a grey-green marble obelisk on a two-step pedestal, set on the top of the steep Leukates cliff in Monrepos Park, Vyborg. It was made in the workshop of the Swedish sculptor Erik Göthe and designed by the English architect Charles Heathcote Tatham. Marble plaques with Latin inscriptions were set into the pedestal's niches; the eastern plaque, dedicated to Auguste-César, and the knight's-helmet reliefs at the base are lost.

The obelisk was commissioned by Baron Paul Nicolay after the early death of his wife Alexandra Simplicia, née de Broglie, whose brothers Auguste-César (1783–1805) and Charles-François (1788–1813) fell at Austerlitz and Kulm as lieutenants in Russian guards regiments. The English architect Charles Heathcote Tatham designed it, and the Swedish sculptor Erik Gustaf Göthe made the monument, erected in 1827 on the Leukas cliff where Nicolay's Temple of Cupid had stood since 1805–1806.

The obelisk's Latin inscriptions render the brothers' names as Augustus and Carolus Broglio, a Latinised form of the French de Broglie. The family name itself varies across sources as Broglie, Broglio, Broïli or de Broglie-Revel, and the monument is also called the obelisk of the Broglie brothers. The cliff beneath it, Leukas Rock, is named after the Greek island of Lefkada.

The obelisk sits along paved pathways within the park and is easily accessible on foot, surrounded by trees and open green areas. The park provides parking and seating areas where visitors can spend time in the outdoors before or after viewing the monument.

The obelisk stands on Leukas Rock, named by Ludwig Heinrich von Nicolay after the Greek island of Lefkada, where Sappho is said to have leapt to her death. From 1805 to 1806 a pavilion called the Temple of Cupid stood on the same spot until it decayed and was replaced by the monument.