Ultrafast molecular separation  (UMS) membranes  are  highly  selective  towards  active organic molecules such as antibiotics, amino acids and proteins that are 0.5-5 nm wide while  lacking a phase  transition  and  requiring  a  low  energy  input  to  achieve  high  speed  separation.  These advantages  are  the  keys  for  deploying UMS membranes in a plethora of  industries,  including petrochemical,  food,  pharmaceutical,  and  water  treatment   industries,  especially  for  dilute system separations. Most recently, advanced nanotechnology and  cutting-edge  nanomaterials have been combined with membrane separation technologies to generate tremendous potential for  accelerating  the  development   of  UMS  membranes.  It  is  therefore  critical  to  update  the 

broader scientific community on the important advances in this exciting, interdisciplinary field. This  review  emphasizes  the  unique  separation  capabilities  of  UMS  membranes,  theories underpinning  UMS  membranes,  traditional polymeric materials and  nanomaterials  emerging on the horizon  for advanced UMS membrane  fabrication and technical applications toaddress the  existing  knowledge  gap.  This  work  includes  detailed  discussions  regarding  existing challenges, as well as perspectives on this promising field.