Llanelwedd ([ɬanˈɛlwɛð]) is a village and community near Builth Wells, in Powys, Wales. It lies within the historic county of Radnorshire. Llanelwedd features the Royal Welsh Showground.

Llanelwedd is on the right bank of the Wye concentrated immediately north of Builth Wells. Here meet the A470 (from Rhayader), the A483 (from Llandrindod Wells and Welshpool), and the A481 (from Worcester). Being more populous, Builth dominates in the general perception of the area, and Llanelwedd's main network of streets can be perceived as part of the town rather than its own village.

A station named after its neighbour, Builth Wells, was opened in the village on the former Mid-Wales Railway from Newtown to Brecon which ran through the village. This has since closed and nothing remains. The former site is used to access the fairground. The nearest mainline station is now Builth Road which is around two miles away.

The local stone is suitable for various uses, and the Llanelwedd Quarries dominate the landscape on the north-east side of the village.

The community includes the hamlets of Llanfaredd and Builth Road.

A Llanelwedd electoral ward exists, which includes the communities of Llanelwedd, Aberedw and Glascwm. At the 2011 Census this ward had a population of 1,206. Since 1999 the ward has elected a county councillor to Powys County Council.

Llanelwedd is the site of the Royal Welsh Showground, which hosts a number of attractions during the year as well as the show. It hosted the National Eisteddfod in 1993.

The village church is at the east end of the village, near the junction of the A481 and A483.