It looks a bit like an old iPhone 30-pin connector.

What's the car make/model/year?

Does that cable join into a wiring loom under the seat?

Some older cars had CD stackers mounted under the passenger seat, but usually the connectors were much bulkier for those.

Behodar:

 

It looks a bit like an old iPhone 30-pin connector.

 

My thoughts also....   

Do you have a screen in the car ? ANy other plugs etc under the seat ?

I just ripped out the TV system that was in my fathers car, not usable for anything anymore - was amazing how many plugs the thing had....

Jap Import?

its likely for one of their automatic toll system components and its been removed

Hey thanks for all the replies, appreciate it! 
What's the car make/model/year?

It's an 05 Mazda Axela. 

Does that cable join into a wiring loom under the seat?

No hopefully this pic shows it better

Do you have a screen in the car ? ANy other plugs etc under the seat ?

No and no. :)

Dumb question probably but if it is an iPhone 30-pin connector, would there be any adapters for them?! (to be able to charge my phone via micro usb perhaps?)

Unfortunately don't have an iphone to try it!

iPod/iPhone 30 pin is most likley. You could get an adapter that would trick the stero into thinking it was playing from a CD Stacker, but was really an iPod. Probably what this is.

Looks more like an old charger for Korean phones / mp3 players (might well have been for Japanese as well)

https://www.amazon.com/Charger-Data-Cable-iRiver-Player/dp/B017GUAC90 

https://www.aliexpress.com/item/32768933704.html

Had them when I lived in korea for the pre smart phone phones and mp3 players such as iriver.  Around 2010

3.5mm AUX Male to 30-pin Female Audio Adapter Cable

One of these should be ok to see if it works eh?

Thanks again!

jjnz1: I cant find the YouTube video, but earlier this year I watched how a company crushes cars that have been involved in accidents.

They connected a computer to a connector similar to the one you found but instead of it being under the passenger seat it was more tucked under the passenger side of the centre console, then lowered a massive air curtain around the car that was vented, then the computer automatically explodes all the airbags inside the car.i think the car was a BMW though.

Summary, the connector was used to explode all airbags before the car went to be crushed.

The OBD2 connector? it's much bigger than that, usually found under the dash somewhere. 

kevinr123:

 

 

3.5mm AUX Male to 30-pin Female Audio Adapter Cable

 

One of these should be ok to see if it works eh?

 

Thanks again!

 

If it's what i think it is, then i think it needs to detect their is an iPod plugged in, so may not work with a straight aux adapter. Get a cheap ipod off trademe and fill it with music might be your best bet if you want to use it. 

Definitely an iPod/iPhone 30 Pin Dock Connector

everettpsycho: I got one of these years ago from a local seller when I was in the UK to convert an old iPod dock to Bluetooth for my android phone.

https://m.aliexpress.com/item/32624196086.html?

If you need Bluetooth adding to your car or night be worth a try. It sometimes had some funny behaviour with some docks where it would shut off as if it wasn't connected but it was very hit and miss what docks it worked consistently with.

Hey that's a great idea, thanks!
Is that more likely to work than the 30pin to aux cable as above? as lxsw20 said "it needs to detect their is an iPod plugged in, so may not work with a straight aux adapter".... so I spose that would do the job?