This chapter dives into the ethical, legal, and societal implications (ELSI) of emerging neurotechnologies, including brain–computer interfaces (BCIs) and deep brain stimulation (DBS). As these technologies advance, they raise critical questions about mental privacy, cognitive liberty, and the potential commercialization of brain data. The chapter examines how BCIs, designed to assist individuals with neurological disorders, may also present risks related to autonomy, informed consent, and the manipulation of cognitive functions. Ethical concerns regarding the protection of personal brain data, especially in vulnerable populations such as children and individuals with cognitive impairments, are highlighted. Furthermore, the chapter explores the existing legal frameworks governing neurotechnological devices, emphasizing the gaps in regulation, particularly regarding data privacy and liability in the event of device failure or misuse. Discussions also focus on the commercialization of brain data, addressing issues of ownership, consent, and the potential commodification of cognitive processes. By critically analyzing these concerns, the chapter underscores the need for robust ethical guidelines and regulatory policies to safeguard mental privacy, protect individual autonomy, and ensure that neurotechnological innovations align with broader societal values. Through a multidisciplinary lens, the chapter invites readers to consider the profound ethical and legal challenges posed by the integration of neurotechnology into society.