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Circular linked lists have either the head or the tail pointing to each other such that the list does not have a beginning nor an end (or rather the two coincide). It is possible to have a singly-linked circular list as well as, more commonly, a doubly circular linked list.

$\begin{tikzpicture}[list/.style={rectangle split, rectangle split parts=3, draw, rectangle split horizontal}, >=stealth, start chain, square/.style={rectangle, draw}] % \node[on chain,draw,inner sep=6pt] (X) {\scriptsize\texttt{null}}; \node[list,on chain] (A) {\nodepart{second} $a$}; \node[list,on chain] (B) {\nodepart{second} $b$}; \node[list,on chain] (C) {\nodepart{second} $c$}; %\node[on chain,draw,inner sep=6pt] (D) {\scriptsize\texttt{null}}; \path[*->] let \p1 = (A.three), \p2 = (A.center) in (\x1,\y2) edge [bend left] (B); \path[*->] let \p1 = (B.three), \p2 = (B.center) in (\x1,\y2) edge [bend left] (C); %\draw[*->] let \p1 = (C.three), \p2 = (C.center) in (\x1,\y2) -- (D); \path[*->] let \p1 = (C.one), \p2 = (C.one) in (\x1,\y2) edge [bend left] (B); \path[*->] let \p1 = (B.one), \p2 = (B.one) in (\x1,\y2) edge [bend left] (A); \path[*->] let \p1 = (C.three), \p2 = (C.center) in (\x1,\y2) edge [in=100,out=100] (A); \path[*->] let \p1 = (A.one), \p2 = (A.center) in (\x1,\y2) edge [in=-100,out=-100] (C); \end{tikzpicture}$