The name comes from Saint Peris, an obscure sixth-century Welsh saint who is supposed to have settled the original cell here - llan-Peris, "the church-enclosure of Peris." His well still bubbles up at Nant Peris, the smaller village at the head of the Llanberis Pass which technically forms part of the same community. The present St Padarn's Church in Llanberis carries a Grade II* listing, as does the smaller chapel of Capel Coch. Above the village, on a rocky knoll between the two lakes Padarn and Peris, the round keep of Dolbadarn Castle still stands. Llywelyn the Great built it in the early thirteenth century to control the head of the pass. Historian Richard Avent considered its keep "the finest surviving example of a Welsh round tower." Edward I took it in 1284 and stripped some of its timbers to build his new fortress at Caernarfon. Later it became a manor house. By the eighteenth and nineteenth centuries the ruin was a destination for landscape painters - Richard Wilson and J. M. W. Turner both came here to paint the castle and the lakes beyond.

In the eighteenth century Llanberis was home to one of the most remarkable women in Welsh popular tradition: Marged ferch Ifan, known throughout North Wales for sheer physical strength. She was a harpist, a fiddler, a hunter, a boat builder, a wrestler, and (in her seventies) reportedly still able to throw any man in the parish. Contemporary accounts describe her wrestling pinches, bare-knuckle bouts, and a string of legends involving her capacity to row boats, build them, and outpull men twice her size. She kept her own pack of hounds. She made her own iron shoes. The historical record is patchy, the legends extensive; what is clear is that she was a real person, that she lived in or near Llanberis, and that her reputation for strength was unusual enough that travellers wrote home about her.

Llanberis became a town in the modern sense because of slate. The Dinorwic Quarry, just up the hill above Llyn Peris, employed more than 3,000 men at its peak in the late nineteenth century. The Padarn Railway carried slate down the lake to Port Dinorwic. The Snowdon Mountain Railway - opened in 1896, a Swiss-built rack-and-pinion line - climbed from the village to the summit of Snowdon and is the only public rack railway in the United Kingdom. Today the National Slate Museum occupies the old quarry workshops at Gilfach Ddu; the Llanberis Lake Railway runs along the trackbed of the old Padarn line for tourist trips; Electric Mountain - the visitor centre for the Dinorwig pumped storage power station - sits beside the road. The Llanberis Path from the village is the longest but least strenuous route up Snowdon, mostly following the railway line. It is, by some margin, the most-walked mountain path in Wales.

Llanberis Mountain Rescue Team handles 150-200 incidents a year, more than any other team in the country. They cover Snowdon - which has its share of inexperienced walkers in trainers carrying half a litre of water - and the surrounding ranges. The team operates out of a small headquarters in the village; most members are volunteers; in a busy summer they can be called out three times in a day. Their fundraising drives are quietly heroic. The village is also home to the Llanberis Mountain Film Festival, founded in 2004 and held annually in February until it went on hiatus in 2019. The Slateman Triathlon - swim in Llyn Padarn, cycle up to Capel Curig, run in the mountains - brings 2,000 athletes here every spring; the Snowdonia Marathon starts and finishes in the village every October.

Llanberis is one of the few places in Snowdonia where you hear Welsh spoken on the street, in the shops, and by children playing along the lake. It is also one of the few villages in Britain that combines a thriving outdoor-sports industry, an industrial-heritage tourism site, and a significant working farming community in roughly equal proportion. Notable former residents include the poet Griffith Williams (Gutyn Peris) and Marc Lloyd Williams, the all-time top scorer of the Cymru Premier with 319 goals in 576 club matches. Twinned with Morbegno in Italian Lombardy. From a flight passing west toward Anglesey, the village shows as a thin ribbon of slate roofs along the south shore of Llyn Padarn, with Snowdon's massif rising directly behind. The geometry of the place has not really changed since Turner painted it.