Seiwa can refer to:

• Emperor Seiwa, emperor of Japan
• Seiwa, Mie, a district in Mie, Japan

• Richard Dease
• Richard De Baptiste
• Richard DeBaptiste
• Richard de Beauchamp, 13th Earl of Warwick
• Richard de Beauchamp, 1st Earl of Worcester
• Richard de Billingford
• Richard de Bokyngeham
• Richard Debrunner
• Richard de Brythampton
• Richard de Burgh, Earl of Ulster
• Richard de Clare, Earl of Pembroke
• Richard de Douvres
• Richard de Gloucester
• Richard de Hoghton
• Richard Deitz
• Richard Delbruck
• Richard de Ledrede
• Richard de Moravia
• Richard de Morville, Constable of Scotland
• Richard Dennen
• Richard Denys
• Richard Depoorter
• Richard de Pulesdon
• Richard Derek Leaman
• Richard de Saint-Victor