```python
class ListNode:
    """Definition for singly-linked list node."""
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next


def reverse_linked_list(head: ListNode) -> ListNode:
    """
    Reverses a singly linked list and returns the new head.
    
    Args:
        head: The head node of the singly linked list.
        
    Returns:
        The head node of the reversed linked list.
    """
    prev = None
    current = head
    
    while current:
        next_node = current.next  # Store the next node
        current.next = prev       # Reverse the link
        prev = current            # Move prev forward
        current = next_node       # Move current forward
    
    return prev  # prev is the new head of the reversed list
```