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),
- Cardinal (Argynnis pandora),
- Niobe Fritillary (Argynnis niobe),
- Dark Green Fritillary (Speyeria aglaja),
- Weaver`s Fritillary (Boloria dia), 
- Small Pearl-bordered Fritillary (Boloria selene),
- 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.

Macin Mountains, Tulcea County, Romania, 22 May 2018