NOTE: This answer changes SHA1s, so take care when using it on a branch that has already been pushed. If you only want to fix the spelling of a name or update an old email, git lets you do this without rewriting history using .mailmap. See my other answer.
Using Interactive Rebase
You could do
git rebase -i -p <some HEAD before all of your bad commits>
Then mark all of your bad commits as "edit" in the rebase file. If you also want to change your first commit, you have to manually add it as the first line in the rebase file (follow the format of the other lines). Then, when git asks you to amend each commit, do
git commit --amend --author "New Author Name <email@address.com>"
edit or just close the editor that opens, and then do
git rebase --continue
to continue the rebase.
You could skip opening the editor altogether here by appending --no-edit
so that the command will be:
git commit --amend --author "New Author Name <email@address.com>" --no-edit && \
git rebase --continue
Single Commit
As some of the commenters have noted, if you just want to change the most recent commit, the rebase command is not necessary. Just do
git commit --amend --author "New Author Name <email@address.com>"
This will change the author to the name specified, but the committer will be set to your configured user in git config user.name and git config user.email. If you want to set the committer to something you specify, this will set both the author and the committer:
git -c user.name="New Author Name" -c user.email=email@address.com commit --amend --reset-author
Note on Merge Commits
There was a slight flaw in my original response. If there are any merge commits between the current HEAD and your <some HEAD before all your bad commits>, then git rebase will flatten them (and by the way, if you use GitHub pull requests, there are going to be a ton of merge commits in your history). This can very often lead to a very different history (as duplicate changes may be "rebased out"), and in the worst case, it can lead to git rebase asking you to resolve difficult merge conflicts (which were likely already resolved in the merge commits). The solution is to use the -p flag to git rebase, which will preserve the merge structure of your history. The manpage for git rebase warns that using -p and -i can lead to issues, but in the BUGS section it says "Editing commits and rewording their commit messages should work fine."
I've added -p to the above command. For the case where you're just changing the most recent commit, this is not an issue.
Update for modern git clients (July 2020)
Use --rebase-merges instead of -p (-p is deprecated and has serious issues).
With version 2.13 of Git and later, --recurse-submodules can be used instead of --recursive:
git clone --recurse-submodules -j8 git://github.com/foo/bar.git
cd bar
Editor’s note: -j8 is an optional performance optimization that became available in version 2.8, and fetches up to 8 submodules at a time in parallel — see man git-clone.
With version 1.9 of Git up until version 2.12 (-j flag only available in version 2.8+):
git clone --recursive -j8 git://github.com/foo/bar.git
cd bar
With version 1.6.5 of Git and later, you can use:
git clone --recursive git://github.com/foo/bar.git
cd bar
For already cloned repos, or older Git versions, use:
git clone git://github.com/foo/bar.git
cd bar
git submodule update --init --recursive
Best Answer
You can do this.
refer the manual here