Siwan

Siwan may refer to
 * Sivan, a month of the Hebrew calendar
 * The Welsh form of Joan (first name)
 * Siwan or Joan, Lady of Wales, the wife and consort of Llywelyn the Great, Prince of Wales
 * Siwan (play), by Saunders Lewis
 * Sewant, beads used as a currency by Native Americans
 * Siwan (album), a musical orchestra project by Jon Balke, and featuring Amina Alaoui

India

 * Siwan District, in the state of Bihar, India
 * Siwan, Bihar, the headquarters of the Siwan district
 * Siwan Subdivision, a subdivision of Siwan district
 * Siwan block, a Community development block in Siwan district
 * Siwan (Lok Sabha constituency), a parliamentary constituency in Bihar, India
 * Siwan (Vidhan Sabha constituency), a Legislative constituency in Bihar, India
 * Siwan Junction, a railway junction station in the state of Bihar, India

People

 * People with given name Siwan
 * Siwan, a Korean singer, member of boy group ZE:A
 * Siwan Morris, Welsh actress