To me, it looks like a "leaf" off of a Christmas or Easter Cactus.

It would help if you could post photos of the entire plant but at a wild guess, I'd say some sort of epiphyllum or orchid cactus.

Reminds me of pitaya or dragonfruit.

Is the leaf flat or lobed?

P.S. I was on my phone before, now on my desktop, and can see the photo a lot more clearly, and I don't see lobes, so not pitaya.

My first thoought was Christmas Cactus

Too long for Christmas or Easter imo. I'd go with Epiphyllum. But a picture of the parent plant would be really helpful.

Here are some epiphyllum that I have

You can see branches here that are similar.

Here is a photo of pitaya (dragon fruit), which as you can see has three sided branches instead of flat ones:

Carol is talking about the segments being 3-angled rather than flat. With Selenicereus undatus producing thick sections that make a cross shape when looked at from the end. If instead the mystery plant is an orchid cactus, then by far the most seen and asked about, passalong kind is Disocactus x jenkinsonii. Otherwise, without flowers being seen it is always possible a yet-to-be-identified orchid cactus plant is one of a great many other named hybrid kinds that have been grown mostly by enthusiasts.

Selenicereus undatus - Wikipedia

Disocactus × jenkinsonii - Wikipedia

Lars is correct! We both grow epi's. Link to photos

If you plant the end/tip of that leaf in moist soil...it will grow a new plant.

If i plant this branch, wi will it grow??

Here you go:

Night Blooming Cereus

Rusty

Oh interesting, Rusty! I have pitaya, and thought night blooming cereus had similar leaves, but now I see it really looks more like the OP image.

Here's a recent photo of my night blooming cereus (Queen of the Night epiphyllum):

The branches have a reddish tint to them that the regular day blooming epiphyllum usually do not have, but otherwise they are somewhat difficult to tell apart, just from the leaves.

The QOTN flowers are very fragrant (and not in the best way IMO), unlike the other epiphyllum, and each flower only lasts one night, although mine blooms two or three times a year, and as you can see, not all buds open on the same night.

Thanks for all you responses, i think it is a Orchid Cactus. 😊

Epiphyllum oxypetalum

@ Lars - might the red tint on yours be a nutrient deficiency? I think a lack of phosphorus can do that...?

Sometimes, the foliage take on a reddish tint when grown in full sun.

Not the biggest fan of xerophytic cacti in general, save for hardy Opuntia and the columnar genus, Cereus..., but I absolutely LOVE, LOVE, LOVE all tropical and epiphytic species of cacti.