DUBAI, July 25 (Reuters) - Saudi Arabia's government has hired Goldman Sachs to manage the sale of a stake in Riyadh airport, the first major privatisation of an airport in the kingdom, three sources familiar with the matter said.

The Saudi Civil Aviation Holding Co plans to sell a minority stake in the Riyadh's King Khalid International Airport, the sources said, adding the stake size could be significant.

The estimated size or value of the stake was not immediately known, but Riyadh has the second biggest airport in Saudi Arabia after Jeddah's King Abdulziz International Airport.

Saudi Civil Aviation Holding Co did not immediately respond to a Reuters query for a comment, while a Goldman Sachs spokesman in London declined to comment.

(Reporting by Saeed Azhar, Hadeel Al Sayegh and Tom Arnold, editing by Louise Heaven) ((Saeed.Azhar@thomsonreuters.com; +65-64035664 ; Reuters Messaging: saeed.azhar.reuters.com@reuters.net))