Hi, I'm new to The Forest speedrunning and I'm wondering if I die in the middle of a run, and continue to the end of it, does it invalidate the run?

No if you die, it doesn't gonna cancel your run. It could be a good way to save time too.

In fact, it's actually utilized during a lot of the any% runs. If you watch one of the top runs, we usually take a fast death when we grab the key card in normal / peaceful / hardmode.

Thanks :)