Jessica Biel and "Transformers" hottie Isabel Lucas have just committed to go to Tanzania to conquer Africa's highest peak in early January ... and of course, it's all for a good cause.
The two are part of a program called Summit on the Summit -- an effort to raise awareness for clean water. There's a rumor that Biel's BF, Justin Tiimberlake will also join in on the climb ... but really, that would seriously screw up the ratio.