thumb|250 px|Ekebyholm Manor (Ekebyholms slott)
Count Arvid Bernhard Horn af Ekebyholm (6 April 166418 April 1742) was a Swedish general, diplomat and politician, a member of the noble Horn family. He served twice as president of the privy council chancellery (1710–1719 and 1720–1738) and was one of the leading figures of the Swedish Age of Liberty.
Soldier and diplomat
Arvid Bernhard Horn was born at Vuorentaka Manor in Halikko (now Salo, Finland).
Politician
In 1705 Horn was made a privy councillor and in 1706 a count. In 1708, he was given oversight of Charles XII's nephew, Charles Frederick, Duke of Holstein-Gottorp (1700–1739), who was under the guardianship of his grandmother Hedwig Eleonora of Holstein-Gottorp (1636–1715) following the death of his mother Hedvig Sophia of Sweden (1681–1708).
In 1710 Horn succeeded Nils Gyldenstolpe as president of the privy council chancellery. Transferred to the central point of the administration, he had ample opportunity of regarding with other eyes the situation of the kingdom, and in consequence of his remonstrances he fell rapidly in the favour of Charles XII. Both in 1710 and 1713 Horn was in favour of summoning the Estates, but when in 1714 the diet adopted an anti-monarchical attitude, he gravely warned and ultimately dissolved it. In Charles XII's later years Horn had little to do with the administration. After the death of Charles XII, in 1718 it was Horn who persuaded Princess Ulrika Eleonora of Sweden (1688–1741) to be elected Queen of Sweden after she had agreed to renounce the powers of absolute monarchy established by her father, King Charles XI. However, he later protested against the queen's autocratic behaviour and resigned from the privy council.
Horn's strong hand kept the inevitable strife of the parliamentary factions within due limits, and it was entirely owing to his provident care that Sweden so rapidly recovered from the wretched condition in which the wars of Charles XII had plunged her. In his foreign policy Horn was extremely wary and cautious, yet without compromising either the independence or the self-respect of his country. He was, however, the promoter of a new principle of administration which in later days proved very dangerous to Sweden under ministers less capable than he was.
For the remainder of his life, Horn lived in retirement at his estate at Ekebyholm Manor (Ekebyholms slott) at Norrtälje.