Hiltrude was born in the early eighth century into a Frankish noble family of the Hainaut borderlands. Her mother was Ada (Ade), her father Wibert, Count of Poitiers and cousin of Pepin the Short; he held estates between the Sambre and the Meuse and founded the Abbey of Liessies about 751. Her brother Guntrad (Gontrad, Gunthard) became the first abbot; she also had a sister named Berthe.
Her parents wished her to marry a powerful Burgundian lord. Hiltrude, however, longed for the religious life. With the blessing of the bishop of Cambrai she took the veil. The rejected suitor married her sister instead. Her brother then gave her a cell attached to the abbey chapel, where she lived as a nun and recluse, sharing the liturgical prayer of the community while practicing the strictest asceticism. Her parents settled upon her for life an estate running from Molhain to Yeaux.
Inspired by her example, several daughters of local lords joined her, so that in 752 a women's annex was established beside the monastery. Hiltrude remained at its head until her death. She died on 27 September, traditionally dated 769 (or toward the end of the eighth century), and was first buried near the village church beside her brother.
Her reputation for sanctity grew through the centuries. On 17 September 1004 Bishop Erluino of Cambrai opened her tomb and elevated her relics. Abbot Louis de Blois later fostered the cult. In 1587 her skull was placed in a silver reliquary. During the Thirty Years' War the relics were carried for safety to Mons and set in an urn in 1641; though the shrine was destroyed in 1793, the relics remain at Liessies. In the eleventh century she was already held to work many miracles, especially among the people of Rance, Trélon, Anor and neighboring places. She is portrayed as a virgin holding a lamp and candle and is invoked against fever; the church of Sainte-Hiltrude in the Avesnois still bears her name.
May Saint Hiltrude obtain for us the grace of single-hearted virginity and steadfast monastic fidelity, that we may prefer the love of Christ to every earthly claim.