| Ælfthryth of Wessex | |
| Succession: | Countess consort of Flanders |
| Reign: | 893/899 – 918 |
| Consort: | yes |
| House: | Wessex |
| Father: | Alfred the Great |
| Mother: | Ealhswith |
| Spouse: | Baldwin II, Count of Flanders |
| Issue: | Arnulf I of Flanders Adalulf, Count of Boulogne Ealswid Ermentrud |
| Death Date: | 7 June 929 |
Ælfthryth of Wessex (c. 877 – 7 June 929), also known as Elftrudis (Elftrude, Elfrida), was an English princess and a countess consort of Flanders to Baldwin II.
She was the youngest daughter of Alfred the Great, the Saxon King of England and his wife Ealhswith. Her siblings included King Edward the Elder and Æthelflæd.
Between 893 and 899, Ælfthryth married Baldwin II (died 918), Count of Flanders.
They had the following issue:
.