费城染色体（英语：Philadelphia chromosome, Ph (or Ph') chromosome），或称费城染色体易位（英语：Philadelphia translocation），是一种与慢性粒细胞性白血病（chronic myelogenous leukemia, CML）相关的特殊染色体易位现象。其中细胞的9号染色体长臂与22号染色体短臂进行相互易位，具体定义为t(9;22)(q34;q11)。这一染色体易位现象与慢性粒细胞性白血病有高度的灵敏度，有95%的慢性粒细胞性白血病患者被检测有此染色体易位（剩余的人群则是或存在一种G显带染色体制备过程中的隐形易位，或是存在其他多变的染色体易位情况）。但是，其对诊断是否为慢性粒细胞性白血病没有足够高的特异度，因为此染色体变异亦发现于急性白血病中（大约20-30%的成人与2-10%的未成年患者案例）以及个别的急性骨髓性白血病案例。

The Philadelphia chromosome or Philadelphia translocation is a specific genetic abnormality in chromosome 22 of leukemia cancer cells (particularly chronic myelogenous leukemia (CML) cells). This chromosome is defective and unusually short because of reciprocal translocation of genetic material between chromosome 9 and chromosome 22, and contains a fusion gene called BCR-ABL1. This gene is the ABL1 gene of chromosome 9 juxtaposed onto the BCR gene of chromosome 22, coding for a hybrid protein: a tyrosine kinase signalling protein that is "always on", causing the cell to divide uncontrollably.