Waldemar Tully (von) Oxholm (11 November 1805 – 3 August 1876) was a Danish nobleman, diplomat, and senior court official. He served as Lord Marshal of the Court under Christian IX from 1863 until his death, and although never in executive office, he is regarded as an influential intermediary in Denmark's transition from absolutism to constitutional monarchy, particularly during the political crises of 1848 and 1863.
Born in Copenhagen, the son of Governor-General Peter Lotharius Oxholm and Ann O’Neill, he was educated at Herlufsholm School and the University of Copenhagen. He joined the Foot Guards in 1821 and spent the following decade in the Danish West Indies, where he assisted in managing his family's plantations on Saint Croix and served as adjutant to Governor-General Peter von Scholten. Returning to Copenhagen in 1834, he assisted Scholten in government deliberations on the abolition of slavery, and was that year appointed tutor to Prince Christian of Glücksburg (later Christian IX), whom he accompanied to the University of Bonn, where a lifelong relationship of trust was established.
After his return to Denmark, Oxholm entered court service as chamberlain (1840) and later chief of the Crown Prince Frederick's household (1842–1847). During the March Revolution of 1848 he mediated between King Frederick VII, Count Adam Wilhelm Moltke, and the National Liberal leaders in forming the March Ministry, subsequently sitting in the Danish Constituent Assembly (1848–1849) and the Landsting (1849–1853). At the outset of the First Schleswig War, he was sent on diplomatic missions to St Petersburg, Stockholm, and London, and served as Danish minister to Britain from 1854 to 1857.
In 1863 Oxholm accompanied Prince Christian and Princess Louise to London for the marriage of Princess Alexandra to the Prince of Wales, where he transmitted the British proposal that Prince William of Denmark should be elected King of Greece. Following Christian IX's accession in November 1863, Oxholm was appointed Lord Marshal of the Court (Danish: overhofmarskal), becoming chief officer of the royal household and principal adviser to the new king. During the constitutional crisis of December 1863, when the recently enacted November Constitution provoked international opposition and the threat of war with Prussia and Austria, he coordinated communication between the crown and the government. Regarded by the National Liberals with suspicion but respected in conservative circles for his loyalty and integrity, he remained one of Christian IX's most trusted advisers until his death at Smidstrup near Vedbæk, aged 70, on 3 August 1876.