Yes, it is a Clematis and a very pretty one too. But I can't tell you the species/cultivar.

I don't think it is a clematis. Looks more like a "Passiflora". Can you post some close-up pictures of the leaves and vines.

I agree with floral_uk that it's a clematis, both from the blossoms and from the leaves and vines visible in the photo.

I'm certain it is a Clematis, not a Passiflora. Compare with C x aromatica. I'm not saying that is what this one is but just to see a similar Clematis.

Here is a link that might be useful: C aromatica

Hello,

I think your clematis might be either C. tashiroi or C. smilacifolia.
You can google both names and compare pics to your plant.