The Shropshire Triathlon attracts triathletes from across the country and beyond and provides a welcome boost for cafes, pubs and shops in the area.
This year the event is also hosting the Sprint Triathlon British Championships with the elite competitors the first to set off on Sunday morning..
Organised by UK Triathlon Shropshire Triathlon sees entrants swim in Ellesmere's mere before cycling on local roads and then run along a closed lane and through the mere's Cremorne Gardens.
While the sprint distance takes in a 750 metre swim, cycling 20 kilometres then running five kilometres, the Shropshire Triathlon also has the Olympic and Middle distance categories.
Earlier this year the mere played host to the UK Triathlon Ultimate Triathlon with entrants swimming on the Friday, cycling on the Saturday and running on the Sunday.
Alderford lake near Whitchurch also plays host to a UK Triathlon event in June.
Keith Hancock, race director, said Ellesmere always welcomed triathletes and their spectators.
Many spend the weekend in the area using local B&Bs, hotels or campsites and spending money in the town.
Local organisations and groups also benefit, receiving donations in return for voluntary help on the day.
Last weekend the town hosted two smaller events, the Ellesmere 10k - hundreds of competitors running through the town - and the mere mile with swimming taking the plunge in the mere.