There are quite a few orange butterflies in Europe, although different in size, with very similar black markings:
- High Brown Fritillary (Argynnis adippe), 
- Silver-washed Fritillary (Argynnis paphia),
- Niobe Fritillary (Argynnis niobe),
- Dark Green Fritillary (Speyeria aglaja),
- Weaver`s Fritillary (Boloria dia), 
- Small Pearl-bordered Fritillary (Boloria selene),
- Marbled Fritillary (Brenthis daphne),
- Lesser Marbled Fritillary (Brenthis ino),
- Queen of Spain Fritillary (Issoria lathonia), 
- Knapweed Fritillary (Melitaea phoebe),
- Spotted Fritillary (Melitaea didyma),
- Heath Fritillary (Melitaea athalia),
- Southern Heath Fritillary (Melitaea celadussa), and
- Glanville Fritillary (Melitaea cinxia).

The best way to distinguish them from each other is by looking at the underside of the hindwings.
Most of them have small white spots or other distinguised markings on the underside of the hindwings.

1st, 2nd & 3rd photo: Cheia Gorge area, Constanta County, Romania, 21 May 2018
4th & 5th photo: Macin Mountains, Tulcea County, Romania, 22 May 2018