3氦过程是3个氦原子核（α粒子）转换成碳原子核的过程。

这种核融合反应可以在超过一亿度K的高温和氦含量丰富的恒星内部迅速的发生。同样的，它发生在较老年，经由质子-质子链反应和碳氮氧循环产生的氦，累积在核心的恒星。在核心的氢已经燃烧完后，核心将塌缩，直到温度达到氦燃烧的燃点。

这个过程释放出的净能量为7.275 MeV。

在第一个阶段形成的Be是不稳定的，会经历2.6×10秒就再分裂回氦，但是在氦燃烧能形成Be的条件下，只要有微小的平衡丰度，就能再捕获一个氦原子核形成C。这种结合三个氦原子核转换成碳的过程就称为3氦过程。

The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon.

Older stars start to accumulate helium produced by the proton–proton chain reaction and the carbon–nitrogen–oxygen cycle in their cores. The products of further nuclear fusion reactions of helium with hydrogen or another helium nucleus produce lithium-5 and beryllium-8 respectively, both of which are highly unstable and decay almost instantly back into smaller nuclei. When the star starts to run out of hydrogen to fuse, the core of the star begins to collapse until the central temperature rises to 10 K (8.6 keV). At this point helium nuclei begin to fuse together faster than their product, beryllium-8, decays back into two helium nuclei.