Weldon was the son of Sir Anthony Weldon of Swanscombe, Kent. He was admitted at Jesus College, Cambridge on 24 November 1620. He became a commander in the Parliamentary Army at Taunton, Somerset, and took part in the siege of Bristol in 1645. He gave up his command to become Governor of Plymouth in 1645.
- Hopper, Andrew J. "Weldon, Ralph". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/28992. (Subscription or UK public library membership required.)
- "Weldon, Ralph (WLDN620R)". A Cambridge Alumni Database. University of Cambridge.
- Willis, Browne (1750). Notitia Parliamentaria, Part II: A Series or Lists of the Representatives in the several Parliaments held from the Reformation 1541, to the Restoration 1660 ... London. pp. 229–239.