What are some examples of Sophocles’ use of dramatic irony in his play Oedipus Rex?

“Dramatic irony” has been briefly and helpfully defined at
dictionary.com as follows:

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irony that is inherent in speeches or a situation
of a drama and is understood by the audience but not grasped by the characters in the
play.

Sophocles’ tragedy
Oedipus Rex displays numerous examples of dramatic irony, including
the following:

• At one point Oedipus declares
  that the man who killed Laius may also kill Oedipus (167-69; Ian Johnston translation;
  see link below). He does not know, of course, that he is the man who killed Laius,
  although anyone familiar with the Oedipus legend would know
  this.


• Oedipus ironically proclaims that by avenging Laius
  he will serve himself (170).


• Oedipus vows to discover the
  criminal lest a “common ruin” afflict Thebes (177). Of course, by discovering the
  criminal (himself) he ruins his own life.


• At one point
  Oedipus declares,

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If someone knows the killer is a
stranger,

from some other state, let him not stay mute.
(268-69)

Oedipus, of course, was originally not from
Thebes.

• Oedipus
  declares that the killer of Laius is the cause of the city’s “pollution” (281), not
  realizing, of course, that he is the killer of
  Laius.


• Oedipus hopes that the killer of Laius will suffer
  “the worst of agonies” (287) – a fate, of course, that will eventually be his
  own.


• Oedipus
  says,

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. . . I pray, too,
that, if he should
become an honoured guest
in my own home and with my
knowledge,                                
I may suffer all those things I’ve
just called down
upon the killers.
(288-92)

The dramatic irony
of this prayer should be obvious.

• Oedipus notes
  that he is now married to Laius’s wife, not realizing, of course, that this woman is his
  own mother (303).


• Oedipus laments that “fate swooped
  down” on Laius’s head (308), not realizing that fate is about to swoop down on his own
  head.


• When Tiresias will not tell Oedipus what Tiresias
  knows about the killing, Oedipus calls him the “most disgraceful of disgraceful men!”
  (399) – a description that will later fit Oedipus himself especially
  well.


• Oedipus accuses Tiresias of having had some role in
  Laius’s death – an ironic accusation if there ever was one
  (412-17).


• Tiresias tells Oedipus that someday the
  latter’s eyes will be dark (505-06), but there is no way at this point for Oedipus to
  realize that he will later blind himself.


• Tiresias
  reveals many specific details about the killer’s identity (546-59), but Oedipus cannot
  see (as the audience can) how these details are relevant to his own
  life.


• Oedipus accuses Creon of having killed Laius (640),
  not realizing that he himself is the killer.

As
should be obvious by now, the specific dramatic ironies that exist in Oedipus
Rex are almost too numerous to list, making it one of the most ironic plays
ever written. Anyone who reads the play for a second time or who knows the Oedipus
legend before reading it cannot help but be struck by the tremendous number of
particular dramatic ironies the play reveals.