周期蛋白依赖性激酶或周期素依赖性激酶（英语：Cyclin-dependent kinases，CDKs）是一个蛋白质激酶家族，因其在细胞周期中的调控作用而首次被发现，该蛋白家族也涉及转录调控、mRNA加工和神经细胞的分化。这类酶存在于已知所有真核生物中，其在细胞周期中的调控作用在进化中相当保守。事实上，酵母细胞的CDK基因被人类的同源基因替换后仍可以正常生长分裂。CDK还是相对较小的蛋白，其分子量在34到40千道尔顿之间，包含有多个激酶结构域。

如其名称，CDK的激酶调控活性依赖于周期素。在没有周期素的情况下，CDK几乎没有激酶活性，只有周期素-CDK复合物才是有活性的激酶。CDK磷酸化其底物的丝氨酸/苏氨酸残基，因此属于丝氨酸/苏氨酸激酶类。CDK的磷酸化位点的共有氨基酸串行为*Ser/Thr-Pro-X-Lys/Arg（其中X为任意氨基酸，*为磷酸化位点，/表示两种氨基酸皆可）。

Cyclin-dependent kinases (CDKs) are a family of protein kinases first discovered for their role in regulating the cell cycle. They are also involved in regulating transcription, mRNA processing, and the differentiation of nerve cells. They are present in all known eukaryotes, and their regulatory function in the cell cycle has been evolutionarily conserved. In fact, yeast cells can proliferate normally when their CDK gene has been replaced with the homologous human gene. CDKs are relatively small proteins, with molecular weights ranging from 34 to 40 kDa, and contain little more than the kinase domain. By definition, a CDK binds a regulatory protein called a cyclin. Without cyclin, CDK has little kinase activity; only the cyclin-CDK complex is an active kinase. CDKs phosphorylate their substrates on serines and threonines, so they are serine-threonine kinases. The consensus sequence for the phosphorylation site in the amino acid sequence of a CDK substrate is [S/T*]PX[K/R], where S/T* is the phosphorylated serine or threonine, P is proline, X is any amino acid, K is lysine, and R is arginine.