脑电图（Electroencephalography, EEG）是通过医学仪器脑电图描记仪，将人体脑部自身产生的微弱生物电于头皮处收集，并放大记录而得到的曲线图。脑电图测量来自大脑中神经元的离子电流产生的电压波动。脑电图用于辅助诊断脑部相关疾病，但因为其易受到干扰，故临床上通常要结合其他手段来使用。

脑电图最常用于诊断癫痫，因为癫痫会导致异常的脑电图读数。它也被用于诊断睡眠障碍，昏迷，脑血管疾病等，和脑死。脑电波曾经是被用于诊断肿瘤，中风和其他局灶性脑疾病的第一线方法，但这种使用已经随着高分辨率解剖成像技术的出现而减少，例如磁共振成像（MRI）和计算机断层扫描（CT）。尽管空间分辨率是有限的，脑电图仍然是用于研究和诊断的宝贵工具，特别是当需要毫秒范围的时间分辨率（CT或MRI是不可能实现）。

Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity of the brain. It is typically noninvasive, with the electrodes placed along the scalp, although invasive electrodes are sometimes used in specific applications. EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time, as recorded from multiple electrodes placed on the scalp. Diagnostic applications generally focus on the spectral content of EEG, that is, the type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals.