  Extreme space weather events including $\ge$X5.0 flares, ground level
enhancement (GLE) events and super geomagnetic storms (Dst $\le$ -250 nT)
caused by super active regions (SARs) during solar cycles 21-24 were studied.
The total number of $\ge$X5.0 solar flares was 62, 41 of them were X5.0-X9.9
flares and 21 of them were $\ge$X10.0 flares. We found that 83.9\% of the
$\ge$X5.0 flares were produced by SARs. 78.05\% of the X5.0-X9.9 and 95.24\% of
the $\ge$X10.0 solar flares were produced by SARs. 46 GLEs registered during
solar cycles 21-24, and 25 GLEs were caused by SARs, indicating that 54.3\% of
the GLEs were caused by SARs. 24 super geomagnetic storms were recorded during
solar cycles 21-24, and 12 of them were caused by SARs, namely 50\% of the
super geomagnetic storms are caused by SARs. It is found that only 29 SARs can
produce $\ge$X5.0 flares, 15 SARs can produce GLEs and 10 SARs can produce
super geomagnetic storms. Of the 51 SARs, only 33 SARs can produce at least one
extreme space weather event, while none of the rest 18 SARs can produce an
extreme space weather event. There were only 4 SARs, each of them can produce
not only a $\ge$X5.0 flare, but also a GLE event and a super geomagnetic storm.
Most of the extreme space weather events caused by the SARs appeared during
solar cycles 22 and 23, especially for GLE events and super geomagnetic storms.
The longitudinal distributions of source locations for the extreme space
weather events caused by SARs were also studied.
