diff --git a/src/main.cpp b/src/main.cpp
index c80a4ac92..44d96d614 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -100,6 +100,7 @@ struct IteratorComparator
 struct COrphanTx {
     CTransaction tx;
     NodeId fromPeer;
+    int64_t nTimeExpire;
 };
 map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(cs_main);
 map<COutPoint, set<map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(cs_main);
@@ -641,7 +642,7 @@ bool AddOrphanTx(const CTransaction& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(c
         return false;
     }
 
-    auto ret = mapOrphanTransactions.emplace(hash, COrphanTx{tx, peer});
+    auto ret = mapOrphanTransactions.emplace(hash, COrphanTx{tx, peer, GetTime() + ORPHAN_TX_EXPIRE_TIME});
     assert(ret.second);
     BOOST_FOREACH(const CTxIn& txin, tx.vin) {
         mapOrphanTransactionsByPrev[txin.prevout].insert(ret.first);
@@ -689,6 +690,26 @@ void EraseOrphansFor(NodeId peer)
 unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
     unsigned int nEvicted = 0;
+    static int64_t nNextSweep;
+    int64_t nNow = GetTime();
+    if (nNextSweep <= nNow) {
+        // Sweep out expired orphan pool entries:
+        int nErased = 0;
+        int64_t nMinExpTime = nNow + ORPHAN_TX_EXPIRE_TIME - ORPHAN_TX_EXPIRE_INTERVAL;
+        map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
+        while (iter != mapOrphanTransactions.end())
+        {
+            map<uint256, COrphanTx>::iterator maybeErase = iter++;
+            if (maybeErase->second.nTimeExpire <= nNow) {
+                nErased += EraseOrphanTx(maybeErase->second.tx.GetHash());
+            } else {
+                nMinExpTime = std::min(maybeErase->second.nTimeExpire, nMinExpTime);
+            }
+        }
+        // Sweep again 5 minutes after the next entry that expires in order to batch the linear scan.
+        nNextSweep = nMinExpTime + ORPHAN_TX_EXPIRE_INTERVAL;
+        if (nErased > 0) LogPrint("mempool", "Erased %d orphan tx due to expiration\n", nErased);
+    }
     while (mapOrphanTransactions.size() > nMaxOrphans)
     {
         // Evict a random orphan:
diff --git a/src/main.h b/src/main.h
index 9b99ae7c8..191aafe04 100644
--- a/src/main.h
+++ b/src/main.h
@@ -56,6 +56,10 @@ static const CAmount HIGH_TX_FEE_PER_KB = 0.01 * COIN;
 static const CAmount HIGH_MAX_TX_FEE = 100 * HIGH_TX_FEE_PER_KB;
 /** Default for -maxorphantx, maximum number of orphan transactions kept in memory */
 static const unsigned int DEFAULT_MAX_ORPHAN_TRANSACTIONS = 100;
+/** Expiration time for orphan transactions in seconds */
+static const int64_t ORPHAN_TX_EXPIRE_TIME = 20 * 60;
+/** Minimum time between orphan transactions expire time checks in seconds */
+static const int64_t ORPHAN_TX_EXPIRE_INTERVAL = 5 * 60;
 /** Default for -limitancestorcount, max number of in-mempool ancestors */
 static const unsigned int DEFAULT_ANCESTOR_LIMIT = 25;
 /** Default for -limitancestorsize, maximum kilobytes of tx + all in-mempool ancestors */