The closest beach to Arnaia (Mainland Halkidiki) is Stratoni Beach, 19.9 km away. Ordered by distance from Arnaia. Photos, map, reviews.
19.9 km from Arnaia

24.7 km from Arnaia

26.8 km from Arnaia

30.1 km from Arnaia

31.1 km from Arnaia

31.2 km from Arnaia

32.4 km from Arnaia

32.8 km from Arnaia

33.0 km from Arnaia

33.2 km from Arnaia

33.6 km from Arnaia

33.9 km from Arnaia

Stratoni Beach, just 19.9 km from Arnaia. The rest are listed below, ordered by distance.
None sit within 15 km of Arnaia itself, but Mainland Halkidiki has 21 beaches in total — listed below, closest first.
Based on user reviews: Psakoudia Beach (★3.8), Karagatsia (★3.8), Kalopigado (★3.8).
The beaches are spread out around Arnaia. A car makes exploring much easier — local buses and taxis are limited outside peak season.
Arnaia is on the Mainland Halkidiki side of Halkidiki, in northern Greece. The nearest airport is Thessaloniki (SKG); from there a car is the most convenient way to reach the Mainland Halkidiki villages.