When can an infant usually sit up unassisted?

Typically, an infant is able to sit up unassisted around 6 months of age. At this stage in development, babies have gained sufficient muscle strength and control to maintain an upright position without support.

During the months leading up to this milestone, infants build the necessary trunk and neck strength through activities such as tummy time and reaching for objects. While some may be able to sit briefly with support around 4 months, it is not until about 6 months that they can sit without any assistance for extended periods. This is an important milestone as it signifies increased core strength and stability, which are crucial for further development in gross motor skills.