Mahāyāna, which translates to "Greater Vehicle," is a branch of Buddhism that emerged around the 1st century CE. It is rooted in the teachings of the historical Buddha, Siddhartha Gautama, but also incorporates new beliefs and practices. The relationship between Mahāyāna and the historical Buddha is a complex and nuanced one, as Mahāyāna holds the Buddha in high regard while also expanding upon his teachings.

Mahāyāna Buddhism sees the historical Buddha as a great teacher who achieved enlightenment and taught others how to do the same. However, Mahāyāna also believes that the Buddha was a manifestation of a primordial, enlightened being known as a bodhisattva. This belief is based on the Mahāyāna concept of the "three bodies of the Buddha," which states that the Buddha has three forms: the Dharmakāya (ultimate reality), the Saṃbhogakāya (celestial form), and the Nirmāṇakāya (physical form). According to Mahāyāna, the historical Buddha was the Nirmāṇakāya form, which means he was a physical manifestation of the ultimate reality.

Mahāyāna also holds the historical Buddha in high regard for his teachings on the Four Noble Truths and the Eightfold Path. However, Mahāyāna expands upon these teachings by emphasizing the importance of compassion and the bodhisattva path. The bodhisattva path is the path to enlightenment taken by those who strive to become bodhisattvas, or beings who have achieved enlightenment but choose to remain in the cycle of rebirth to help others attain enlightenment as well. This path is seen as the ultimate expression of compassion, as bodhisattvas dedicate themselves to the well-being and enlightenment of all beings.

In addition to the teachings of the historical Buddha, Mahāyāna also incorporates new scriptures, known as sūtras, that were believed to be teachings of the Buddha but were not included in the early Buddhist canon. These sūtras, such as the Lotus Sūtra and the Heart Sūtra, emphasize the importance of compassion and the bodhisattva path.

Overall, the relationship between Mahāyāna and the historical Buddha can be seen as one of reverence and expansion. Mahāyāna holds the Buddha in high regard as a great teacher and enlightened being, while also expanding upon his teachings to emphasize compassion and the bodhisattva path. This relationship highlights the evolution and growth of Buddhism as it spread to different regions and cultures, adapting and incorporating new beliefs and practices while still holding the historical Buddha in high esteem.