The Avonmore River (Irish: An Abhainn Mhór, meaning "the big river") flows approximately 30 km southward from Lough Dan in the Wicklow Mountains, passing through Annamoe, Laragh, and Rathdrum before joining the Avonbeg River at the Meeting of the Waters to form the River Avoca. The river drains a heavily wooded valley and passes through the grounds of Avondale House, the former home of Charles Stewart Parnell, near Rathdrum.

The river is typically paddled in three sections. The longest begins at the bridge at Lough Dan, accessed by turning right at the main crossroads in Roundwood and following signs for Lough Dan adventure centre. The regular section puts in at the bridge in Annamoe village, reached via the R755 regional road. The shortest section begins at Trooperstown Wood, approximately 3.2 km from Annamoe in the direction of Glendalough, where a left turn leads to a bridge put-in. The take-out for the lower sections is at the Meeting of the Waters.

The river grades range from II+ through to IV and above depending on water level and section. The Rathdrum to Meeting of the Waters section runs approximately 7.5 km at grade 2+, best paddled at medium-high water or above, and is considered a useful progression river between grade 2+ and grade 3. It features multiple waves, micro eddies, and a series of drops with pools below, making it practical for lapping individual features. A road runs alongside this section, providing straightforward access and egress.

The upper sections carry more serious hazards. Jackson's Falls, located just above Laragh, is a significant drop that varies considerably in character with water level, rated IV at low water, IV+ at medium to high water, and V at very high flows due to a dangerous terminal stopper. Scouting is strongly recommended for those unfamiliar with it. A rock known as "Fernando" sits in the middle of the falls and is known to damage boat hulls. The rapid called Guinness', in the Annamoe to Trooperstown section, is also worth scouting, as a mistimed move over its second part can have consequences. The river flows through scenic woodland throughout, and the confluence with the Glenmacnass River at Laragh is a notable landmark along the route.