Can i use my laptop's 65W charger to charge Iphone 15 Pro Max?

Yes you can,

your phone will just let trough the amount needed.

It is perfectly safe i am currently charging with a 65 watt and un good also look online there is multiple sources

Have a nice day

armiterre

See the following from Fast charge your iPhone - Apple Support

To fast charge, you need an iPhone 15 model with a USB-C cable like the one that came in the box or an earlier iPhone model with a USB-C to Lightning cable and one of these adapters:

• Apple 18W,* 20W, 29W, 30W, 35W, 61W, 67W, 87W, or 96W, or 140W USB-C Power Adapter
• A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)